Communicating with a REST API relies on multiple concepts that we'll cover briefly below:
JSONopen in new window: a standard data interchange format used a lot in the HTTP messages of REST APIs.
REST APIopen in new window: it is a standard communication interface between a client and conforms to the constraints of REST architectural style. In a REST API, HTTP messages are stateless and use JSON data format.
HTTP messagesopen in new window: an http message is a textual message that contains different parts and can be either a request or a response. A request is the HTTP message that the client sends to the server and response is the HTTP message that the server sends to the client in reaction to the request. Both requests and responses have a part called a body. In rest APIs, the body is generally formatted in JSON.
Codableopen in new window: it is a type that can convert itself into and out of an external representation. It is equivalent to Serializable in Java. This type is helpful if we want to convert an object into an out of a JSON string.
async and await: these keywords are used to call an asynchronous function using a synchronous coding fashion. This means that callbacks are needed no more!
Swift supports most Object Oriented Programming features:
',4),u=e("li",null,[n("Classes that can be instantiated into objects. "),e("ul",null,[e("li",null,"Constructors and destructors are called initializers and deinitializers respectively.")])],-1),d={href:"https://docs.swift.org/swift-book/LanguageGuide/AccessControl.html",target:"_blank",rel:"noopener noreferrer"},h=e("li",null,"Simple inheritance of classes. Multiple inheritance of classes and is not supported.",-1),f=e("li",null,"Inheritance allows one class to use the characteristics of another.",-1),m={href:"https://levelup.gitconnected.com/polymorphism-in-swift",target:"_blank",rel:"noopener noreferrer"},b={href:"https://www.avanderlee.com/swift/composition-inheritance-code-architecture/",target:"_blank",rel:"noopener noreferrer"},k=e("li",null,"Static methods and properties are supported.",-1),g=e("li",null,"Generic types are supported",-1),w=e("em",null,"Protocols",-1),_=e("em",null,"Interfaces",-1),v=e("li",null,"Classes and structs can conform to multiple protocols.",-1),y={href:"https://www.hackingwithswift.com/articles/74/understanding-protocol-associated-types-and-their-constraints",target:"_blank",rel:"noopener noreferrer"},x=e("li",null,[n("They are used a lot by swift developers to the point that there is a programming technique called "),e("strong",null,"Protocol oriented programming"),n(".")],-1),S=e("p",null,"Here are some additional features:",-1),T=e("ul",null,[e("li",null,[n("Extensions allow to add functions and conform to additional protocols outside of the original class, struct or protocol declaration. This has many uses that simplify our code and here are some examples. "),e("ul",null,[e("li",null,"They can add methods to classes from any library that we can use."),e("li",null,"They can define default implementations in protocols.")])]),e("li",null,"Abstract classes are not available")],-1),q={href:"https://swiftfiddle.com/05f4d4d3c8235299a875e08dcb3992f8",target:"_blank",rel:"noopener noreferrer"},I=e("p",null,"In additions to classes, structs in swift are powerful and provide similar features than classes with some exceptions.",-1),E=e("h2",{id:"structs",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#structs"},[e("span",null,"Structs")])],-1),P={href:"https://docs.swift.org/swift-book/LanguageGuide/Subscripts.html",target:"_blank",rel:"noopener noreferrer"},A={href:"https://docs.swift.org/swift-book/LanguageGuide/ClassesAndStructures.html",target:"_blank",rel:"noopener noreferrer"},F=e("ul",null,[e("li",null,"Inheritance."),e("li",null,"Type casting (enables you to check and interpret the type of a class instance at runtime)."),e("li",null,"Deinitializers."),e("li",null,"Reference counting allows more than one reference to a class instance (similar to pointers but much less complex to use).")],-1),U={href:"https://swiftfiddle.com/d72ea73dcbae5cc25908c56bdabcf877",target:"_blank",rel:"noopener noreferrer"},C=a(`
This feature seems advanced to understand but since it's used a lot in SwiftUI, let's explore a simple explanation and we'll provide some links to study it further.
In a base level, opaque types allow to return Protocols while keeping the concrete type information known by the compiler. It is enabled by prefixing the type with the some keyword.
Opaque types allow to keep the benefits of abstracting the code on a developer level while maintaining the performance and optimization benefits of concrete typing. In addition to that, they allow the compiler to better handle some cases such as Self or associated type requirements. Please note that explaining all the features that opaque types bring to the code is an advanced topic. For more information and details, please read the articles mentioned in the Sources and more reading section.
For this training, we'll assume that opaque help types the compiler perform better optimizations with protocols, are used in many places in SwiftUI and allow to improve our code in some cases. We'll show below a simple use case where we can define a method that returns an Equatable.
// Source: https://www.educative.io/answers/what-is-opaque-type-in-swift
+
+// create a function that returns some Equatable
+// The compiler fails is the return type is just "Equatable"
+funcmakeInteger()->someEquatable{
+ Int.random(in:0...10)
+}
+
+let firstInteger =makeInteger()
+let secondInteger =makeInteger()
+
+// this returns "false" because they are of the same concrete type else, Xcode will scream at us.
+print(firstInteger == secondInteger)
+
+funcmakeString()->someEquatable{
+ "A String"
+}
+let firstString =makeString()
+
+// Compiler error because the concrete type is not the same.
+print(firstInteger == firstString)
+
`,6),j={href:"https://github.com/apple/swift-evolution/blob/main/proposals/0244-opaque-result-types.md",target:"_blank",rel:"noopener noreferrer"},G={href:"https://github.com/apple/swift-evolution/blob/main/proposals/0341-opaque-parameters.md",target:"_blank",rel:"noopener noreferrer"},O=e("h2",{id:"use-structs-by-default",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#use-structs-by-default"},[e("span",null,"Use structs by default")])],-1),W={href:"https://developer.apple.com/documentation/swift/choosing-between-structures-and-classes",target:"_blank",rel:"noopener noreferrer"},z=e("ul",null,[e("li",null,"Use structures by default."),e("li",null,"Use classes when you need Objective-C interoperability."),e("li",null,"Use classes when you need to control the identity of the data you’re modeling."),e("li",null,"Use structures along with protocols to adopt behavior by sharing implementations.")],-1),R=e("p",null,"We note that structures are the default choice mostly because they are value types. This makes the code more predictable because changes cannot come from a parent call. Another advantage of structs is that they are more friendly with functional programming. We'll talk about functional programming in the next section.",-1),L=e("h2",{id:"functional-programming-features",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#functional-programming-features"},[e("span",null,"Functional programming features")])],-1),N={href:"https://flexiple.com/ios/introduction-to-functional-programming-using-swift/",target:"_blank",rel:"noopener noreferrer"},B=e("p",null,"Pure functions are functions that do not have side effects and will thus return always the same output given the same input. Swift allows to create pure functions but does not provide compile time guarantees that a function is pure.",-1),D=e("code",null,"let",-1),K={href:"https://stackoverflow.com/a/24232845",target:"_blank",rel:"noopener noreferrer"},M={href:"https://blog.ndepend.com/declarative-programming-depth/",target:"_blank",rel:"noopener noreferrer"},V={href:"https://swiftfiddle.com/4cebea7bfea3d58600df30f1af325663",target:"_blank",rel:"noopener noreferrer"},H=e("p",null,"Swift has many more features and provides a rich standard library. We'll explore them as needed in the next sections. For now, let's create some UIs in the next chapter.",-1),J=e("h2",{id:"structured-concurrency",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#structured-concurrency"},[e("span",null,"Structured Concurrency")])],-1),Q=e("li",null,"Swift supports writing concurrent code in a structured way.",-1),X=e("li",null,[n("Concurrency means that we execute multiple "),e("strong",null,"tasks"),n(" at the same time. For example, update the UI while the app performs an HTTP request to the server.")],-1),Y=e("li",null,[n("In Swift, we can create concurrent Tasks with the "),e("code",null,"Task"),n(", "),e("code",null,"TaskGroup"),n(" types.")],-1),Z={href:"https://swiftfiddle.com/ce6995e6f1cd9c0fb226df7995b546a5",target:"_blank",rel:"noopener noreferrer"},$={href:"https://oleb.net/2021/structured-concurrency",target:"_blank",rel:"noopener noreferrer"},ee=a("
Structured concurrency means that we write concurrent code using the usual control flow structures (as opposed to callback-based concurrent code)
In Swift is possible through the async and await keywords.
When we await a Task, the control flow will continue when it end without blocking the Task or TaskGroup on which it is launched.
A function that has uses the await keyword must be declared as async
",1),ne=e("li",null,[n("To summarize "),e("code",null,"async and await"),n(" + "),e("code",null,"Task"),n(" and "),e("code",null,"TaskGroup"),n(" = "),e("strong",null,"Structured Concurrency")],-1),se=e("li",null,"Continuations allow to convert callback code into async/await",-1),te={href:"https://swiftfiddle.com/c34b73f3b260192f63bd8159b9853986",target:"_blank",rel:"noopener noreferrer"},ae={href:"https://swiftfiddle.com/93183f842d0d02756b3e911e9ddc24b8",target:"_blank",rel:"noopener noreferrer"},oe={href:"https://swiftfiddle.com/d5c9039422d60ce14f307623a3d9107e",target:"_blank",rel:"noopener noreferrer"},ie={href:"https://swiftfiddle.com/d62a161afcd623615a27fb09a8b2dc5c",target:"_blank",rel:"noopener noreferrer"},re=a(`
Structured Concurrency in Playground Book
// Reference: https://stackoverflow.com/a/24066317
+importPlaygroundSupport
+
+//Playground does not stop at the end of the code
+PlaygroundPage.current.needsIndefiniteExecution =true
+
+funcsampleFunc()async{
+ print("sampleFunc")
+ try?awaitTask.sleep(until:.now +.seconds(2))
+}
+
+Task{
+ awaitsampleFunc()
+ print("done")
+ // End the playground
+ PlaygroundPage.current.finishExecution()
+}
+
Generics allow to pass a type as a parameter to a class, struct, enum or function.
A type parameter can be declares with <T> where T is the type parameter.
Examples
func printArray<T>(array: [T]) { for item in array { print(item) } }
Swift can infer the type of the parameter if it is not provided and if it's not ambiguous.
`,3),le={href:"https://swiftfiddle.com/c2619f36b41875606075e1f4baf2b93a",target:"_blank",rel:"noopener noreferrer"},ce=e("h2",{id:"key-paths",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#key-paths"},[e("span",null,"Key-paths")])],-1),pe={href:"https://docs.swift.org/swift-book/documentation/the-swift-programming-language/expressions/#Key-Path-Expression",target:"_blank",rel:"noopener noreferrer"},ue=e("li",null,[n("They are created with the "),e("code",null,"\\.propertyName"),n(" syntax.")],-1),de=e("li",null,"They are often used to sort, filter, group and map collections and in SwiftUI to bind properties to UI elements.",-1),he={href:"https://swiftfiddle.com/9a220108db372f3c2063d4d7275001a9",target:"_blank",rel:"noopener noreferrer"},fe=e("h2",{id:"exercises",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#exercises"},[e("span",null,"Exercises")])],-1),me=e("h3",{id:"exercise-1",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#exercise-1"},[e("span",null,"Exercise 1")])],-1),be={href:"https://swiftfiddle.com/5d65286d3db0ccf08f7ca3bf1cef31fe",target:"_blank",rel:"noopener noreferrer"},ke={class:"custom-container details"},ge=e("summary",null,"Please open to see the solution(s)",-1),we={href:"https://swiftfiddle.com/41469e54bc7c025b003341a0e96f16a3",target:"_blank",rel:"noopener noreferrer"},_e=e("h3",{id:"exercise-2",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#exercise-2"},[e("span",null,"Exercise 2")])],-1),ve={href:"https://swiftfiddle.com/43fc226645abb5457d26c7176fb6009d",target:"_blank",rel:"noopener noreferrer"},ye={class:"custom-container details"},xe=e("summary",null,"Please open to see the solution(s)",-1),Se={href:"https://swiftfiddle.com/a1227e17989ad80da5137a31aa6dfbeb",target:"_blank",rel:"noopener noreferrer"},Te=e("h3",{id:"exercise-3",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#exercise-3"},[e("span",null,"Exercise 3")])],-1),qe={href:"https://swiftfiddle.com/d225e7e3b061035b6a1987c3cf2fb3d5",target:"_blank",rel:"noopener noreferrer"},Ie={class:"custom-container details"},Ee=e("summary",null,"Please open to see the solution(s)",-1),Pe={href:"https://swiftfiddle.com/b45e785e8d832058e394f179782b214c",target:"_blank",rel:"noopener noreferrer"},Ae={href:"https://swiftfiddle.com/6aac1fb721c00c565509dded883f7481",target:"_blank",rel:"noopener noreferrer"},Fe=e("h2",{id:"sources-and-more-reading",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#sources-and-more-reading"},[e("span",null,"Sources and more reading")])],-1),Ue={href:"https://docs.swift.org",target:"_blank",rel:"noopener noreferrer"},Ce={href:"https://tanaschita.com/20220206-understanding-opaque-types-in-swift/",target:"_blank",rel:"noopener noreferrer"},je={href:"https://github.com/apple/swift-evolution/blob/main/proposals/0244-opaque-result-types.md",target:"_blank",rel:"noopener noreferrer"},Ge={href:"https://async-await-in-swift.netlify.app/",target:"_blank",rel:"noopener noreferrer"},Oe={href:"https://github.com/SwiftFiddle/swiftfiddle-web/discussions/101",target:"_blank",rel:"noopener noreferrer"};function We(ze,Re){const s=i("ExternalLinkIcon");return r(),l("div",null,[p,e("ul",null,[u,e("li",null,[n("Encapsulation and "),e("a",d,[n("4 access levels"),t(s)]),n(" that range from private to public")]),h,f,e("li",null,[n("Method overriding and "),e("a",m,[n("polymorphism"),t(s)]),n(" and access control.")]),e("li",null,[n("Overloading of operators and functions, "),e("a",b,[n("composition"),t(s)]),n(".")]),k,g,e("li",null,[w,n(" which are the equivalent of "),_,n(". "),e("ul",null,[v,e("li",null,[n("Protocols can have "),e("a",y,[n("associated types"),t(s)]),n(" which is similar to generic types.")]),x])])]),S,T,e("p",null,[e("a",q,[n("this code"),t(s)]),n(" illustrates some of the above features.")]),I,E,e("p",null,[n("In Swift, structs have many similar features with classes. They support properties, methods, "),e("a",P,[n("subscripts"),t(s)]),n(", initializers, extensions and conforming to protocols. The features that are only available in classes "),e("a",A,[n("are as follows"),t(s)]),n(":")]),F,e("p",null,[e("a",U,[n("this code"),t(s)]),n(" sample shows how to use structs with protocols.")]),C,e("p",null,[n("As of Swift 5.1 "),e("a",j,[n("opaque types are only available for return values"),t(s)]),n(". As of Swift 5.7 "),e("a",G,[n("opaque arguments have been implemented"),t(s)])]),O,e("p",null,[n("As surprising as it seems, Apple recommends using "),e("a",W,[n("structs by default instead of classes"),t(s)]),n(". More precisely, when we want to add a new data type, we should not assume that it should be a class by default and check if a structure is more relevant. Apple provides the following recommendations:")]),z,R,L,e("p",null,[n("Functional programming revolves around "),e("a",N,[n("three main concepts"),t(s)]),n(": pure functions, immutable objects and declarative programming.")]),B,e("p",null,[n("Immutable objects can be created using classes or structs with constant properties (declared with "),D,n("). As mentioned above, structs are recommended by default "),e("a",K,[n("and here are other good reasons"),t(s)]),n(". One of the most notable ones is that since structs are passed around by value, thus they help us avoiding side effects.")]),e("p",null,[n("Declarative programming can be easily explained as a way of programming that is centered "),e("a",M,[n("around telling what to do and not how to do it"),t(s)]),n(". This allows to obtain a clearer and more maintainable code than traditional imperative programming. For example, when we want to filter a table, a for loop is not declarative (we say imperative in this case) while the WHERE SQL syntax is considered declarative. Declarative programing is possible in Swift through chaining functions and passing functions as arguments. Indeed, as we have seen earlier, Swift has 1st class support for functions. In addition to that, we can find declarative APIs in the standard Swift library and in Swift UI. The latter will be explored in a different chapter. For now, let's illustrate "),e("a",V,[n("with this code"),t(s)]),n(" how to process a list of strings using only declarative APIs provided by Swift.")]),H,J,e("ul",null,[Q,X,Y,e("li",null,[n("Without Structured concurrency, we would use complex concepts to such as callbacks which make code less readable (have you lived the "),e("a",Z,[n("callback hell"),t(s)]),n(" ?).")]),e("li",null,[n("We say that a code is "),e("a",$,[n("structured"),t(s)]),n(" when we use the well-know control flow structures :if/then/else, loops, functions, lexical scopes for variables. "),ee]),ne,se]),e("p",null,[n("This swift script shows a sample of using "),e("a",te,[n("Task + async/await"),t(s)])]),e("p",null,[n("This swift script shows a sample of using "),e("a",ae,[n("TaskGoup + async/await"),t(s)])]),e("p",null,[n("This swift script shows a sample of "),e("a",oe,[n("TaskGoup cancellation"),t(s)])]),e("p",null,[n("This swift script shows how to "),e("a",ie,[n("convert callbacks into async/await"),t(s)])]),re,e("p",null,[e("a",le,[n("this code"),t(s)]),n(" illustrates some of the above features.")]),ce,e("ul",null,[e("li",null,[e("a",pe,[n("Key-paths"),t(s)]),n(" allow to refer to properties of a type.")]),ue,de]),e("p",null,[e("a",he,[n("this code"),t(s)]),n(" illustrates some of the above features.")]),fe,me,e("p",null,[e("a",be,[n("Please click on this link to view the exercise"),t(s)])]),e("details",ke,[ge,e("p",null,[e("a",we,[n("Solution"),t(s)])])]),_e,e("p",null,[e("a",ve,[n("Please click on this link to view the exercise"),t(s)])]),e("details",ye,[xe,e("p",null,[e("a",Se,[n("Solution"),t(s)])])]),Te,e("p",null,[e("a",qe,[n("Please click on this link to view the exercise"),t(s)])]),e("details",Ie,[Ee,e("p",null,[e("a",Pe,[n("Solution 1"),t(s)])]),e("p",null,[e("a",Ae,[n("Solution 2 with results"),t(s)])])]),Fe,e("ul",null,[e("li",null,[e("a",Ue,[n("Swift official documentation"),t(s)]),n(".")]),e("li",null,[e("a",Ce,[n("Understanding opaque types in Swift"),t(s)])]),e("li",null,[e("a",je,[n("Swift evolution Opaque Result Types"),t(s)])]),e("li",null,[e("a",Ge,[n("Some async examples on SwiftFiddle"),t(s)]),n(" and "),e("a",Oe,[n("how to use Runloop on SwiftFiddle"),t(s)])])])])}const Ne=o(c,[["render",We],["__file","index.html.vue"]]),Be=JSON.parse('{"path":"/swift-part2/","title":"Swift (part 2)","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"Object oriented programming features","slug":"object-oriented-programming-features","link":"#object-oriented-programming-features","children":[]},{"level":2,"title":"Structs","slug":"structs","link":"#structs","children":[]},{"level":2,"title":"Opaque types","slug":"opaque-types","link":"#opaque-types","children":[]},{"level":2,"title":"Use structs by default","slug":"use-structs-by-default","link":"#use-structs-by-default","children":[]},{"level":2,"title":"Functional programming features","slug":"functional-programming-features","link":"#functional-programming-features","children":[]},{"level":2,"title":"Structured Concurrency","slug":"structured-concurrency","link":"#structured-concurrency","children":[]},{"level":2,"title":"Generics","slug":"generics","link":"#generics","children":[]},{"level":2,"title":"Key-paths","slug":"key-paths","link":"#key-paths","children":[]},{"level":2,"title":"Exercises","slug":"exercises","link":"#exercises","children":[{"level":3,"title":"Exercise 1","slug":"exercise-1","link":"#exercise-1","children":[]},{"level":3,"title":"Exercise 2","slug":"exercise-2","link":"#exercise-2","children":[]},{"level":3,"title":"Exercise 3","slug":"exercise-3","link":"#exercise-3","children":[]}]},{"level":2,"title":"Sources and more reading","slug":"sources-and-more-reading","link":"#sources-and-more-reading","children":[]}],"git":{"updatedTime":1719480969000,"contributors":[{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":7},{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":6}]},"filePathRelative":"swift-part2/README.md"}');export{Ne as comp,Be as data};
diff --git a/assets/index.html-B8dggsdP.js b/assets/index.html-B8dggsdP.js
new file mode 100644
index 0000000..377e5d8
--- /dev/null
+++ b/assets/index.html-B8dggsdP.js
@@ -0,0 +1 @@
+import{_ as i,r as n,o as l,c as r,a as e,b as t,d as a,e as s}from"./app-Bbun9eEO.js";const c={},d=e("h1",{id:"swift-part-1",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#swift-part-1"},[e("span",null,"Swift (part 1)")])],-1),u=e("div",{class:"custom-container tip"},[e("p",{class:"custom-container-title"},"Estimated time"),e("p",null,"1/2 day")],-1),h=e("p",null,"Swift is the official programming language for developing iOS, iPadOS, macOS, watchOS and AppleTV apps. It can also target other platforms such as Windows, Linux and Android.",-1),f={href:"https://github.com/swiftlang/swift",target:"_blank",rel:"noopener noreferrer"},p=s('
Swift has modern and interesting features. Here are some notable ones:
Swift is statically typed and supports implicit typing.
Static typing: types cannot change on runtime (it is the opposite of dynamic typing).
Implicit typing: the compiler can infer the type whenever possible.
var creates mutable variables.
let creates immutable variables or constants.
String interpolation is available with this syntax \\(expression).
Parenthesis are not required in if, for, while and switch statements.
if and switch statements are expressions.
for-each is the only type of for loop available.
Optionals allows to write code free from null pointer errors (also called Null Safety in other languages).
Functional programming is supported (Higher-order functions and functions as 1st class items, etc.).
Object oriented programming is supported.
Interfaces are called protocols and they are used a lot.
Structures are available and provide a lot of features (More on that later).
',3),m={href:"https://swiftfiddle.com/2382a3b3fdc54631140f51bae116dc74",target:"_blank",rel:"noopener noreferrer"},w=e("p",null,"In the following sections, we will delve into more features.",-1),_={class:"custom-container tip"},b=e("p",{class:"custom-container-title"},"++ and -- are removed since swift 3",-1),g={href:"https://github.com/apple/swift-evolution/blob/master/proposals/0004-remove-pre-post-inc-decrement.md",target:"_blank",rel:"noopener noreferrer"},y=s('
In the this section, the terms argument and parameter are used interchangeably.
The declaration of functions in Swift has the following peculiarities:
Parameters are named and ordered. This means that when you call a function, you must specify the name of the arguments in the same order as the declaration.
A parameter can have different external and internal names by declaring it like this: externalName internalName: Type. The external name is also called an argument label.
You can make a parameter anonymous by setting this external name: _.
Arguments can have a default value. These are also called optional arguments.
Swift allows to use functions as first class items or citizens. This allows to store function references into variables, pass functions as arguments to other functions and return a function from a function. Here is a brief listing of the these features:
A function can be assigned to a variable, passed as a function parameter or returned from a function.
A function type can be expressed as follows: (typeOfParam1, typeOfParam2, etc) -> returnType.
The empty return type is Void.
We can use typealias to shorten writing long types.
Swift supports anonymous functions (also called lambda function) with the following syntax { argName1, argName2, etc. in // code }
In a nutshell, optionals is a compiler feature that allows you to avoid the infamous Null pointer exception or npe. The Swift compiler provides null safety and reports errors and warnings when we manipulate nullable (also called optional) values. Here is a list of null safety features provided by swift:
The name of null in iOS development
In Swift, the null value is called nil
All types are non optional by default. This means that we cannot assign nil to a variable or an argument. For example, this code fails var s: String = nil.
A type can be made optional by suffixing it with a ?. For example: var s: String? = nil.
You cannot call a method or a property of an optional type, unless you do one of those possibilities:
Use optional chaining with the ? suffix.
Provide a default value with the ?? operator.
Unwrap the optional so that it becomes non optional.
Force unwrap the optional using the ! suffix. This should never be used as it bypasses compiler checks.
Never unwrap with !
You must never force unwrap with the !. Use other unwrapping techniques instead. On of the rarest exceptions is with Interface builder's Outlets in UIKit @IBOutlet var label: UILabel!. Fortunately, since we are not using UIKit in this training, we will avoid this situation.
Enumerations allow to work with a group of values in a type-safe fashion. Swift provides many interesting features to enumerations:
When the compiler can infer it, you can omit the name of the enumeration when you use one of its values.
Switch statements support enumerations.
You can easily iterate over an enum's values by using : CaseIterable.
You can associate values or provide a raw value to enumeration cases. Raw values can be implicitly assigned.
You can use another enumeration as associated value, this is called recursive enumeration.
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We must call throw when we want to return an error. Throwing in a normal situation is a bad practice.
We say that a function throws when it can throw and exception. It must have the throws qualifier.
When we call a function that throws, we must precede the call with try keyword
When we call a function that throws, we can either propagate its error if it is thrown or handle to stop its propagation.
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The Result type is a an enum that has two possible cases: success(Sucess) or failure(Failure)
The failure value must conform to the Error protocol
A Result can be handled with usual Swift features for enums: guard, switch, etc.
The Result type has can be used with the exception style. Its get() method returns the success value or throws the error.
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For further reading please consult "),e("a",O,[t("the official documentation"),a(o)]),t(".")]),N,A,e("ul",null,[e("li",null,[t("Exceptions provide an alternate return route with the "),P,t(" keyword. "),e("ul",null,[e("li",null,[t("The thrown value must conform the "),q,t(" protocol. We can even throw a "),e("a",F,[t("String"),a(o)]),t(" that way.")]),W])]),R]),e("p",null,[e("a",U,[t("This code"),a(o)]),t(" illustrates error handling features.")]),Y,e("ul",null,[e("li",null,[t("Swift has 3 collection types out of the box: Array, Dictionary and Set. 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Null safety)","slug":"optionals-aka-null-safety","link":"#optionals-aka-null-safety","children":[]},{"level":2,"title":"Enumerations","slug":"enumerations","link":"#enumerations","children":[]},{"level":2,"title":"Error management","slug":"error-management","link":"#error-management","children":[]},{"level":2,"title":"Some features in bulk","slug":"some-features-in-bulk","link":"#some-features-in-bulk","children":[]},{"level":2,"title":"Exercises","slug":"exercises","link":"#exercises","children":[{"level":3,"title":"Exercise 1","slug":"exercise-1","link":"#exercise-1","children":[]},{"level":3,"title":"Exercise 2","slug":"exercise-2","link":"#exercise-2","children":[]},{"level":3,"title":"Exercise 3","slug":"exercise-3","link":"#exercise-3","children":[]}]},{"level":2,"title":"Sources","slug":"sources","link":"#sources","children":[]}],"git":{"updatedTime":1719253649000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":6},{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":5}]},"filePathRelative":"swift-part1/README.md"}');export{re as comp,ce as data};
diff --git a/assets/index.html-C39pB5w2.js b/assets/index.html-C39pB5w2.js
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',4),d={href:"https://developer.apple.com/documentation/",target:"_blank",rel:"noopener noreferrer"},h={href:"https://github.com/worldline/ios-training",target:"_blank",rel:"noopener noreferrer"},p={href:"https://icones8.fr/icon/51974/xcode",target:"_blank",rel:"noopener noreferrer"};function u(f,g){const t=o("ExternalLinkIcon");return s(),r("div",null,[m,e("ul",null,[e("li",null,[e("a",d,[n("Official documentation"),i(t)])]),e("li",null,[e("a",h,[n("GitHub repository for this training"),i(t)])]),e("li",null,[e("a",p,[n("Logo downloaded from icones8"),i(t)])])])])}const b=a(c,[["render",u],["__file","index.html.vue"]]),k=JSON.parse('{"path":"/","title":"Welcome","lang":"en-US","frontmatter":{"home":true,"heroImage":"/logo.png","tagline":"Getting started with iOS development with Swift and SwiftUI","actions":[{"text":"Get started →","link":"/presentation/","type":"primary"}],"features":[{"title":"Swift","details":"Discover the Swift programming language (version 5.10)"},{"title":"SwiftUI","details":"Develop iOS applications"}],"footer":"Worldline, 2021"},"headers":[{"level":2,"title":"Prerequisites","slug":"prerequisites","link":"#prerequisites","children":[]},{"level":2,"title":"Useful links","slug":"useful-links","link":"#useful-links","children":[]}],"git":{"updatedTime":1719246851000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":3},{"name":"yassine benabbas (a527524)","email":"yassine.benabbas@worldline.com","commits":2},{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":2},{"name":"Sowtch","email":"quentin.cptr@gmail.com","commits":1}]},"filePathRelative":"index.md"}');export{b as comp,k as data};
diff --git a/assets/index.html-CfxHtkWF.js b/assets/index.html-CfxHtkWF.js
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`,7),h={href:"https://swiftwasm.org/",target:"_blank",rel:"noopener noreferrer"},p={href:"https://pad.swiftwasm.org/",target:"_blank",rel:"noopener noreferrer"},u={href:"https://github.com/TokamakUI/Tokamak",target:"_blank",rel:"noopener noreferrer"},f={href:"https://github.com/swiftwebui/SwiftWebUI",target:"_blank",rel:"noopener noreferrer"},w=e("h2",{id:"advanced-swift",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#advanced-swift"},[e("span",null,"Advanced Swift")])],-1),m={href:"https://docs.swift.org/swift-book/documentation/the-swift-programming-language/concurrency/#Actors",target:"_blank",rel:"noopener noreferrer"},b={href:"https://developer.apple.com/documentation/Swift/AdoptingSwift6",target:"_blank",rel:"noopener noreferrer"},g={href:"https://docs.swift.org/swift-book/documentation/the-swift-programming-language/attributes/",target:"_blank",rel:"noopener noreferrer"},v={href:"https://docs.swift.org/swift-book/documentation/the-swift-programming-language/macros/",target:"_blank",rel:"noopener noreferrer"},_=e("h2",{id:"conclusion",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#conclusion"},[e("span",null,"Conclusion")])],-1),k=e("p",null,"This training was introduction on Swift and SwiftUI. It just scratched the surface of developing for the Apple development. There are many things that we didn't explore such as the accessibility, hardware features such as geolocation and the technical aspects of the developer account (certificates, provisioning profiles, etc.).",-1),S={href:"https://developer.apple.com/videos/",target:"_blank",rel:"noopener noreferrer"},y={href:"https://www.raywenderlich.com/",target:"_blank",rel:"noopener noreferrer"},I={href:"https://www.hackingwithswift.com/",target:"_blank",rel:"noopener noreferrer"},x={href:"https://developer.apple.com/swift-playgrounds/",target:"_blank",rel:"noopener noreferrer"},T={href:"https://developer.apple.com/tutorials/app-dev-training",target:"_blank",rel:"noopener noreferrer"};function U(A,W){const n=r("ExternalLinkIcon");return s(),i("div",null,[d,e("ul",null,[e("li",null,[e("a",h,[t("SwiftWasm"),o(n)]),t(" is a project that allows to run Swift code in the browser using WebAssembly.")]),e("li",null,[e("a",p,[t("SwiftWasm Pad"),o(n)]),t(" is an online editor that allows to write SwiftUI code and run it in the browser. It relies on the "),e("a",u,[t("TokamakUI"),o(n)]),t(" framework which is SwiftUI-compatbile framework(or a re-implementation of SwiftUI) for the web.")]),e("li",null,[e("a",f,[t("SwiftWebUI"),o(n)]),t(" is another project that allows to run a server that renders SwiftUI to the browser. Note that it is considered as a toy project by its creator.")])]),w,e("ul",null,[e("li",null,[e("a",m,[t("Swift actors"),o(n)])]),e("li",null,[e("a",b,[t("Swift 6 strict concurrency"),o(n)])]),e("li",null,[e("a",g,[t("Attributes"),o(n)])]),e("li",null,[e("a",v,[t("Macros allow to run actions on code at compile time"),o(n)])])]),_,k,e("p",null,[t("To go further, it is advised to watch the videos from Apple's "),e("a",S,[t("WWDC"),o(n)]),t(' (WorldWide Developer Conference - pronounced "dubdub dee cee"). There many other resources available online that you should pick and choose depending on the needs. Here are some of them:')]),e("ul",null,[e("li",null,[e("a",y,[t("raywenderlich.com"),o(n)])]),e("li",null,[e("a",I,[t("hackingwithswift.com"),o(n)])]),e("li",null,[e("a",x,[t("Swift playgrounds"),o(n)])]),e("li",null,[e("a",T,[t("Official iOS App Dev Tutorials"),o(n)])])])])}const N=a(c,[["render",U],["__file","index.html.vue"]]),B=JSON.parse('{"path":"/to-go-further/","title":"Going further","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"Server side development","slug":"server-side-development","link":"#server-side-development","children":[]},{"level":2,"title":"Swift and SwoftUI on the browser","slug":"swift-and-swoftui-on-the-browser","link":"#swift-and-swoftui-on-the-browser","children":[]},{"level":2,"title":"Advanced Swift","slug":"advanced-swift","link":"#advanced-swift","children":[]},{"level":2,"title":"Conclusion","slug":"conclusion","link":"#conclusion","children":[]}],"git":{"updatedTime":1719433280000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":4},{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":3},{"name":"yassine benabbas (a527524)","email":"yassine.benabbas@worldline.com","commits":1}]},"filePathRelative":"to-go-further/README.md"}');export{N as comp,B as data};
diff --git a/assets/index.html-ChAAQVq_.js b/assets/index.html-ChAAQVq_.js
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+import{_ as i,r as n,o as r,c as l,a as e,b as a,d as s,e as o}from"./app-Bbun9eEO.js";const d={},c=e("h1",{id:"locally-persisting-data",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#locally-persisting-data"},[e("span",null,"Locally persisting data")])],-1),p=e("div",{class:"custom-container tip"},[e("p",{class:"custom-container-title"},"Estimated time"),e("p",null,"1/4 day")],-1),h=e("p",null,"Persisting data locally consists of keeping app data after the app has been killed and the variables removed from memory. The persisted data offers many advantages. We can use it to show initial data when the app starts and waits for the first batch data to be fetched from the server. It can also be used to allow for offline app usage.",-1),u={class:"custom-container warning"},f=e("p",{class:"custom-container-title"},"iOS isolates app data from other apps",-1),m={href:"https://medium.com/@dinesh.kachhot/different-ways-to-share-data-between-apps-de75a0a46d4a",target:"_blank",rel:"noopener noreferrer"},b=e("p",null,"There are many ways to persist data in SwiftUI that we cover below.",-1),g=e("h2",{id:"userdefaults",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#userdefaults"},[e("span",null,"UserDefaults")])],-1),v={href:"https://www.hackingwithswift.com/books/ios-swiftui/storing-user-settings-with-userdefaults",target:"_blank",rel:"noopener noreferrer"},w=o(`
Here is sample code that shows how to persist and load data.
A more advanced and powerful technique is to manually load and persist a Codable into a file. This technique is useful if you want to store complex objects (such as the state or model) in a JSON file. There are two steps in this process, the first one consists of decoding / encoding the object from / into JSON using JSONDecoder().decode and JSONEncoder().encode. The second step consists of loading / saving the encoded data and we can think of two ways to achieve this. The first one consists of user defaults' dataForKey: to load the data and setObject:ForKey to persist it. Another one consists of creating and managing a file by the developer using file APIs such as fileHandle.availableData to load the data from a file and data.write to save it.
For storing data in a database or similar fashion, SQLite is available as a low level library. It is not recommended to use it unless there is a strong performance concern. Instead, it is recommended to use libraries specialized in data persistence. Some can be assimilated to an ORM library (Object Relational Mapper). The remainder of this section describes some of them.
Please be careful about the pricing of cloud storage
Sophisticated databases generally provide cloud storage to provide a complete offer. If you're interested in storing data in the cloud, please take some time to read the pricing page to avoid any bad surprises when your app runs in production.
`,8),k={href:"https://developer.apple.com/documentation/coredata",target:"_blank",rel:"noopener noreferrer"},y=e("p",null,"It works similarly as an ORM where classes are mapped into tables. Xcode provides a graphical editor that allows to specify the tables, the relations and generate the necessary code (in Swift or Objective-C).",-1),_=e("figure",null,[e("img",{src:"https://docs-assets.developer.apple.com/published/fbb9767e96/rendered2x-1622022015.png",alt:"Core date editor",tabindex:"0",loading:"lazy"}),e("figcaption",null,"Core date editor")],-1),x={href:"https://www.hackingwithswift.com/books/ios-swiftui/how-to-combine-core-data-and-swiftui",target:"_blank",rel:"noopener noreferrer"},S=e("h3",{id:"realm",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#realm"},[e("span",null,"Realm")])],-1),T={href:"https://realm.io/",target:"_blank",rel:"noopener noreferrer"},C=o('
As opposed to Realm and Core Data, which are local first databases, Firebase datastore is a cloud first database. This means that Firebase Datastore requires an internet connection to store and load the data. However, the library is simple to use and supports real time updates.
TIP
Firebase datastore is part of a bigger suite of service called Firebase. For example, we can Firebase App Distribution in Firebase, which is a service that allows to deploy and distribute apps without going the burden of using TestFlight.
This PW shows how to save a Codable in a manually managed file using JSON encoder and filesystem APIs.
',5),I={href:"https://developer.apple.com/tutorials/app-dev-training/persisting-data",target:"_blank",rel:"noopener noreferrer"};function D(O,F){const t=n("ExternalLinkIcon");return r(),l("div",null,[c,p,h,e("div",u,[f,e("p",null,[a("For security reasons, each app is isolated from the rest of the apps. This is called sandboxing. "),e("a",m,[a("This article"),s(t)]),a(" shows the different ways that allow two or more apps to share their data")])]),b,g,e("p",null,[a("It is a very simple key-value storage that persists data in a file. The API surface is very small and the developer does not need to manage the persisted file. This makes this technique very efficient for simple storage use cases. You can find a short "),e("a",v,[a("guide here"),s(t)]),a(".")]),w,e("p",null,[e("a",k,[a("Core Data"),s(t)]),a(' is the official library to "Persist or cache data on a single device, or sync data to multiple devices with CloudKit". It existed since iOS 3 and Apple continuously updates it to keep it relevant. It also has the reputation of having a steep learning curve, but it remains famous among developers.')]),y,_,e("p",null,[a("Even though Core Date existed before SwiftUI, Apple made sure that both of them can be used together. This article shows "),e("a",x,[a("how to use Core Data in a SwiftUI project"),s(t)]),a(".")]),S,e("p",null,[e("a",T,[a("Realm"),s(t)]),a(" is a high level alternative to SQLite. It can be seen as alternative to Core Data as they seem to provide a similar list of features. Most notably, the possibility to store data locally or in the cloud. The points where Realm wins is that the library seems simpler to learn and to use and that it is also available in Android.")]),C,e("p",null,[e("a",I,[a("https://developer.apple.com/tutorials/app-dev-training/persisting-data"),s(t)])])])}const P=i(d,[["render",D],["__file","index.html.vue"]]),N=JSON.parse('{"path":"/persist-data/","title":"Locally persisting data","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"UserDefaults","slug":"userdefaults","link":"#userdefaults","children":[]},{"level":2,"title":"Codable saved in a file","slug":"codable-saved-in-a-file","link":"#codable-saved-in-a-file","children":[]},{"level":2,"title":"Sophisticated data persistence libraries","slug":"sophisticated-data-persistence-libraries","link":"#sophisticated-data-persistence-libraries","children":[{"level":3,"title":"Core Data","slug":"core-data","link":"#core-data","children":[]},{"level":3,"title":"Realm","slug":"realm","link":"#realm","children":[]},{"level":3,"title":"Firebase datastore (or any other cloud based storage)","slug":"firebase-datastore-or-any-other-cloud-based-storage","link":"#firebase-datastore-or-any-other-cloud-based-storage","children":[]}]},{"level":2,"title":"PW: complete the official iOS persisting data tutorial","slug":"pw-complete-the-official-ios-persisting-data-tutorial","link":"#pw-complete-the-official-ios-persisting-data-tutorial","children":[]}],"git":{"updatedTime":1701178983000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":3}]},"filePathRelative":"persist-data/README.md"}');export{P as comp,N as data};
diff --git a/assets/index.html-Cv2fRjYf.js b/assets/index.html-Cv2fRjYf.js
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Communicating with a REST API relies on multiple concepts that we'll cover briefly below:
',4),u={href:"https://www.json.org/json-en.html",target:"_blank",rel:"noopener noreferrer"},d={href:"https://www.redhat.com/en/topics/api/what-is-a-rest-api",target:"_blank",rel:"noopener noreferrer"},h={href:"https://developer.mozilla.org/en-US/docs/Web/HTTP/Messages",target:"_blank",rel:"noopener noreferrer"},m=e("em",null,"body",-1),f={href:"https://developer.apple.com/documentation/swift/codable",target:"_blank",rel:"noopener noreferrer"},k=e("code",null,"Serializable",-1),b=e("li",null,[e("code",null,"async"),n(" and "),e("code",null,"await"),n(": these keywords are used to call an asynchronous function using a synchronous coding fashion. This means that callbacks are needed no more!")],-1),v={href:"https://developer.apple.com/documentation/foundation/urlsession",target:"_blank",rel:"noopener noreferrer"},_={href:"https://github.com/apple/swift-corelibs-foundation",target:"_blank",rel:"noopener noreferrer"},g=e("h2",{id:"pw-call-a-rest-api",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#pw-call-a-rest-api"},[e("span",null,"PW: call a REST API")])],-1),w={href:"https://www.hackingwithswift.com/books/ios-swiftui/sending-and-receiving-codable-data-with-urlsession-and-swiftui",target:"_blank",rel:"noopener noreferrer"},q={href:"https://itunes.apple.com/search?term=taylor+swift&entity=song",target:"_blank",rel:"noopener noreferrer"},T=t(`
`,1);function y(S,P){const s=r("ExternalLinkIcon");return i(),l("div",null,[c,e("ul",null,[e("li",null,[e("a",u,[n("JSON"),a(s)]),n(": a standard data interchange format used a lot in the HTTP messages of REST APIs.")]),e("li",null,[e("a",d,[n("REST API"),a(s)]),n(": it is a standard communication interface between a client and conforms to the constraints of REST architectural style. In a REST API, HTTP messages are stateless and use JSON data format.")]),e("li",null,[e("a",h,[n("HTTP messages"),a(s)]),n(": an http message is a textual message that contains different parts and can be either a request or a response. A request is the HTTP message that the client sends to the server and response is the HTTP message that the server sends to the client in reaction to the request. Both requests and responses have a part called a "),m,n(". In rest APIs, the body is generally formatted in JSON.")]),e("li",null,[e("a",f,[n("Codable"),a(s)]),n(": it is a type that can convert itself into and out of an external representation. It is equivalent to "),k,n(" in Java. This type is helpful if we want to convert an object into an out of a JSON string.")]),b,e("li",null,[e("a",v,[n("URLSession"),a(s)]),n(": The official iOS HTTP client which is part of the Foundation library. This library is not part of the Swift standard library but there is an implementation for non-Apple platforms which is called "),e("a",_,[n("swift-corelibs-foundation"),a(s)]),n(".")])]),g,e("p",null,[n("This PW relies on the "),e("a",w,[n("excellent tutorial from hackingwithswift"),a(s)]),n(". It guides you on how to fetch JSON data from "),e("a",q,[n("iTunes's API"),a(s)]),n(". Please find and excerpt of the response body below.")]),T])}const x=o(p,[["render",y],["__file","index.html.vue"]]),E=JSON.parse('{"path":"/api-communication/","title":"Communicate with a REST API","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"Some useful concepts","slug":"some-useful-concepts","link":"#some-useful-concepts","children":[]},{"level":2,"title":"PW: call a REST API","slug":"pw-call-a-rest-api","link":"#pw-call-a-rest-api","children":[]}],"git":{"updatedTime":1660750594000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":2}]},"filePathRelative":"api-communication/README.md"}');export{x as comp,E as data};
diff --git a/assets/index.html-DKuyFSlS.js b/assets/index.html-DKuyFSlS.js
new file mode 100644
index 0000000..b1f6828
--- /dev/null
+++ b/assets/index.html-DKuyFSlS.js
@@ -0,0 +1,28 @@
+import{_ as o,r as i,o as l,c,a as n,b as a,d as e,e as t}from"./app-Bbun9eEO.js";const p="/ios-training/assets/swftui-playground-MsNlfoqb.png",r="/ios-training/assets/hello-swiftui-DCdT_J-Q.png",u={},d=t('
Apple provides two official UI frameworks : UIKit and SwiftUI.
UIKit is the originally used framework for UI development. It relies on defining the UI in a separate file (storyboard or xib) and the behavior in a swift file. In 2019, Apple release the first version of SwiftUI.
The remainder of this training focuses on SwiftUI.
SwiftUI brings a new approach to build UIs that we can summarize as follows:
All the UI is defined in Swift code. Neither Storyboards nor xibs are needed anymore.
The UI is defined in a declarative style.
States and bindings allow to hold the app data. The app UI updates automatically when these data change.
UI elements are structs that conform to the View protocol.
Complex views can be defined by breaking them into smaller views. This is called view composition.
The modifier technique is used to apply modifications to a view. A modifier returns a new view each time.
',8),m={href:"https://developer.apple.com/documentation/swiftui",target:"_blank",rel:"noopener noreferrer"},f=n("h2",{id:"prerequisites",tabindex:"-1"},[n("a",{class:"header-anchor",href:"#prerequisites"},[n("span",null,"Prerequisites")])],-1),h={href:"https://www.apple.com/swift/playgrounds/",target:"_blank",rel:"noopener noreferrer"},k={href:"https://swiftui-playground.kishikawakatsumi.com/",target:"_blank",rel:"noopener noreferrer"},v=n("figure",null,[n("img",{src:p,alt:"SwiftUI web playground",tabindex:"0",loading:"lazy"}),n("figcaption",null,"SwiftUI web playground")],-1),w={href:"https://github.com/compnerd/swift-win32",target:"_blank",rel:"noopener noreferrer"},b=t(`
As noted earlier, SwiftUI views are structs that conforms to the View protocol. This protocol defined a computed property that returns a View as an opaque type.
The body of the view has a VStack as its root element. A VStack is a container view that arrange its direct children vertically (on a column). The first child is a Text view and its second child is a Button.
The Text view chains calls to some methods that we call modifiers. They allow to do anything that we want to the view that called it and they return a new View instance. This means that we can apply another modifier to the result of a modifier and so on (this is called chaining). This allows modifiers to have a declarative syntax that makes the code easy to understand. SwiftUI provides built-in modifiers and allows us to create custom ones. Can you match all the modifiers used in the code and their effects ?
The button has no action, meaning that is does nothing on click and its content is defined as an HStack. An HStack is a container view that arrange its direct children horizontally (on a row). The stack contains an image and a button.
The view renders as illustrated by the image below.
@State: Single source of truth of a view and should not be shared with other views.
@Binding: allows to pass a reference of a state to a child view using $state.
@EnvironmentObject: Allows to globally share data between views. An @EnvironmentObject conforms to the ObservableObject protocol and its properties have the @Published property wrapper.
@ObservedObject: Allows to observe changes in an object that conforms to the ObservableObject protocol.
',14),g={href:"https://developer.apple.com/tutorials/swiftui",target:"_blank",rel:"noopener noreferrer"},_=n("p",null,"Please cover these tutorials to get a good grasp of SwiftUI.",-1),y={href:"https://developer.apple.com/tutorials/swiftui/creating-and-combining-views",target:"_blank",rel:"noopener noreferrer"},I={href:"https://developer.apple.com/tutorials/swiftui/building-lists-and-navigation",target:"_blank",rel:"noopener noreferrer"},S={href:"https://developer.apple.com/tutorials/swiftui/handling-user-input",target:"_blank",rel:"noopener noreferrer"},U={href:"https://developer.apple.com/tutorials/swiftui/animating-views-and-transitions",target:"_blank",rel:"noopener noreferrer"},x={href:"https://developer.apple.com/tutorials/swiftui/composing-complex-interfaces",target:"_blank",rel:"noopener noreferrer"},T={href:"https://developer.apple.com/tutorials/swiftui/working-with-ui-controls",target:"_blank",rel:"noopener noreferrer"};function A(q,V){const s=i("ExternalLinkIcon");return l(),c("div",null,[d,n("p",null,[a("The "),n("a",m,[a("official documentation of SwiftUI is available here"),e(s)]),a(".")]),f,n("p",null,[a("It is recommended to use Xcode to learn and create SwiftUI apps. For simple apps, we can use the "),n("a",h,[a("Swift Playgrounds"),e(s)]),a(" app. There is a "),n("a",k,[a("web playground"),e(s)]),a(" that can be exceptionally used. You can see a screenshot of the tool below.")]),v,n("p",null,[a("Another promising alternative to watch is "),n("a",w,[a("compnerd's windows port"),e(s)]),a(" of UIKit and SwiftUI. So, if you can have a recent version Xcode running, this is be the best IDE for SwiftUI development.")]),b,n("p",null,[a("Apple provides a comprehensive "),n("a",g,[a("SwiftUI tutorial"),e(s)]),a(" that covers most of the basic use cases such as creating views and handling inputs, animations and transitions.")]),_,n("ul",null,[n("li",null,[a("Basic layout "),n("ul",null,[n("li",null,[n("a",y,[a("Creating and combining views"),e(s)]),a(" (40 min)")]),n("li",null,[n("a",I,[a("Building lists and navigation"),e(s)]),a(" (35 min)")]),n("li",null,[n("a",S,[a("Handling user input"),e(s)]),a(" (20 min)")])])]),n("li",null,[a("Animations and complex layouts "),n("ul",null,[n("li",null,[n("a",U,[a("Animating views and transitions"),e(s)]),a(" (20 min)")]),n("li",null,[n("a",x,[a("Composing complex interfaces"),e(s)]),a(" (20 min)")]),n("li",null,[n("a",T,[a("Working with UI controls"),e(s)]),a(" (25 min)")])])])])])}const B=o(u,[["render",A],["__file","index.html.vue"]]),E=JSON.parse('{"path":"/ui-development/","title":"UI development","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"SwiftUI","slug":"swiftui","link":"#swiftui","children":[]},{"level":2,"title":"Prerequisites","slug":"prerequisites","link":"#prerequisites","children":[]},{"level":2,"title":"Anatomy of a basic view","slug":"anatomy-of-a-basic-view","link":"#anatomy-of-a-basic-view","children":[]},{"level":2,"title":"A summary of important concepts","slug":"a-summary-of-important-concepts","link":"#a-summary-of-important-concepts","children":[]},{"level":2,"title":"PW: complete some official SwiftUI tutorials","slug":"pw-complete-some-official-swiftui-tutorials","link":"#pw-complete-some-official-swiftui-tutorials","children":[]}],"git":{"updatedTime":1719475184000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":5},{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":1}]},"filePathRelative":"ui-development/README.md"}');export{B as comp,E as data};
diff --git a/assets/index.html-DOlN3MeL.js b/assets/index.html-DOlN3MeL.js
new file mode 100644
index 0000000..28abb77
--- /dev/null
+++ b/assets/index.html-DOlN3MeL.js
@@ -0,0 +1 @@
+import{_ as i,r,o as s,c as l,a as e,b as t,d as a,e as o}from"./app-Bbun9eEO.js";const c="/ios-training/assets/swiftui-framework-wwdc-OMsLBsB_.jpg",p="/ios-training/assets/xcodes-DaBHvxPG.png",d="/ios-training/assets/xcode-new-project-BgcBHlMK.png",h={},f=o('
iOS development consists of developing applications that can target mainly the iPhone and iPad but also macOS, iWatch and Apple TV. There are many ways to achieve this:
Using the official frameworks and tools provided by Apple
Using 3rd party frameworks and tools such as Capacitor, MAUI and Flutter
This training focuses on iOS development using the official tools and frameworks proposed by Apple. Our development stack will consist of the following items:
Programming language: Swift
UI Framework: SwiftUI
IDEs: Xcode and Swift Playgrounds
In addition to that, It is also possible to leverage the Swift language (without SwiftUI) in order to develop console apps and servers on Window, Linux, macOS.
The early days of iOS development used the Objective-C language, the UIKit UI Framework and -the good old- Xcode. This ecosystem was basic but quite powerful and allowed to develop amazing apps. The continuous updates from Apple improved the developer experience. For example, memory management became automatic (thanks to ARC) and the layout system became capable of adapting to different screen sizes.
In WWDC 2014, Apple announced the Swift language as an Open Source modern replacement to Objective-C. Following that, apple announced during the next WWDC SwiftUI as the replacement for UIKit.
swiftui
As of 2021, the majority of new iOS projects use Swift and SwiftUI with UIKit as a fallback for the UI aspects.
',13),u=e("a",{href:""},"Xcodes",-1),g={href:"https://apps.apple.com/us/app/swift-playgrounds/id1496833156?mt=12",target:"_blank",rel:"noopener noreferrer"},m=e("ul",null,[e("li",null,"Xcodes is a tools that downloads and manages the different versions of Xcode.")],-1),w=e("figure",null,[e("img",{src:p,alt:"xcodes",tabindex:"0",loading:"lazy"}),e("figcaption",null,"xcodes")],-1),_={href:"https://swiftforwindows.github.io/",target:"_blank",rel:"noopener noreferrer"},y={href:"https://swift.org/download/#releases",target:"_blank",rel:"noopener noreferrer"},b=e("li",null,"You can use VSCode or Fleet as an IDE.",-1),k={href:"https://github.com/compnerd/swift-win32",target:"_blank",rel:"noopener noreferrer"},S=e("li",null,[t("Open a terminal and run the following command to check if Swift is installed "),e("code",null,"swift --version"),t(".")],-1),v=o('
',6),x={href:"https://swift.org/package-manager/",target:"_blank",rel:"noopener noreferrer"},I=e("li",null,"Xcode projects are projects fully managed by Xcode (.xcodeproj)",-1),O={href:"https://github.com/Carthage/Carthage",target:"_blank",rel:"noopener noreferrer"},C={href:"https://cocoapods.org/",target:"_blank",rel:"noopener noreferrer"},j=e("p",null,"In this training, we'll use swiftpm and Xcode.",-1),U=e("h2",{id:"links-and-references",tabindex:"-1"},[e("a",{class:"header-anchor",href:"#links-and-references"},[e("span",null,"Links and references")])],-1),A={href:"https://9to5mac.com/2019/06/03/apple-announces-swiftui-a-modern-declarative-user-interface-framework-for-apple-platforms/",target:"_blank",rel:"noopener noreferrer"},L={href:"https://www.apple.com/newsroom/2015/12/03Apple-Releases-Swift-as-Open-Source/",target:"_blank",rel:"noopener noreferrer"},P={href:"https://www.sutori.com/en/story/the-history-of-ios-app-development--hzFfwkD2KYLaa5WrxsrUFGMh",target:"_blank",rel:"noopener noreferrer"},W={href:"https://www.timetoast.com/timelines/history-of-ios",target:"_blank",rel:"noopener noreferrer"};function X(T,B){const n=r("ExternalLinkIcon");return s(),l("div",null,[f,e("ul",null,[e("li",null,[t("On macOS, install "),u,t(" and "),e("a",g,[t("Swift Playgrounds"),a(n)]),t(". "),m])]),w,e("ul",null,[e("li",null,[t("For windows and Linux users you can install "),e("a",_,[t("Swift for Windows"),a(n)]),t(" or "),e("a",y,[t("Swift for Ubuntu"),a(n)]),t(". This will allow you to run Swift code on your machine. "),e("ul",null,[b,e("li",null,[t("Unfortunately, SwiftUI development either challenging or not supported. (on Windows you can try to use "),e("a",k,[t("swift-win32"),a(n)]),t(")")])])]),S]),v,e("ul",null,[e("li",null,[t("Official tools: "),e("ul",null,[e("li",null,[e("a",x,[t("Swift Package Manager"),a(n)]),t(" (also called swiftpm) is the official tool to manage Swift projects. It is platform and IDE agnostic.")]),I])]),e("li",null,[t("3rd party tools: "),e("ul",null,[e("li",null,[e("a",O,[t("Carthage"),a(n)])]),e("li",null,[e("a",C,[t("CocoaPods"),a(n)])])])])]),j,U,e("ul",null,[e("li",null,[e("a",A,[t("Apple announces SwiftUI, a modern declarative user interface framework for Apple platforms"),a(n)])]),e("li",null,[e("a",L,[t("Apple Releases Swift as Open Source"),a(n)])]),e("li",null,[e("a",P,[t("The History of iOS App Development (from iOS 1 to 8)"),a(n)])]),e("li",null,[e("a",W,[t("History of iOS from 2007 to 2018"),a(n)])])])])}const F=i(h,[["render",X],["__file","index.html.vue"]]),M=JSON.parse('{"path":"/presentation/","title":"Presentation","lang":"en-US","frontmatter":{},"headers":[{"level":2,"title":"Welcompe the world of iOS development","slug":"welcompe-the-world-of-ios-development","link":"#welcompe-the-world-of-ios-development","children":[]},{"level":2,"title":"History","slug":"history","link":"#history","children":[]},{"level":2,"title":"Getting started","slug":"getting-started","link":"#getting-started","children":[{"level":3,"title":"Create a CLI app with swift CLI","slug":"create-a-cli-app-with-swift-cli","link":"#create-a-cli-app-with-swift-cli","children":[]},{"level":3,"title":"Create an App using Xcode or Swift playgrounds","slug":"create-an-app-using-xcode-or-swift-playgrounds","link":"#create-an-app-using-xcode-or-swift-playgrounds","children":[]}]},{"level":2,"title":"Swift project managers","slug":"swift-project-managers","link":"#swift-project-managers","children":[]},{"level":2,"title":"Links and references","slug":"links-and-references","link":"#links-and-references","children":[]}],"git":{"updatedTime":1719246851000,"contributors":[{"name":"Yassine Benabbas","email":"yassine.benabbas@worldline.com","commits":5},{"name":"yassine benabbas (a527524)","email":"yassine.benabbas@worldline.com","commits":2},{"name":"yostane","email":"1958676+yostane@users.noreply.github.com","commits":1}]},"filePathRelative":"presentation/README.md"}');export{F as comp,M as data};
diff --git a/assets/index.html-z4YYCP43.js b/assets/index.html-z4YYCP43.js
new file mode 100644
index 0000000..b739a10
--- /dev/null
+++ b/assets/index.html-z4YYCP43.js
@@ -0,0 +1,84 @@
+import{_ as i,r as o,o as p,c as l,a as n,b as s,d as t,e}from"./app-Bbun9eEO.js";const c={},u=n("h1",{id:"mini-project",tabindex:"-1"},[n("a",{class:"header-anchor",href:"#mini-project"},[n("span",null,"Mini project")])],-1),r=n("p",null,"The final chapter of this training will ask you to create a SwiftUI app from scratch.",-1),d=n("h2",{id:"requirements",tabindex:"-1"},[n("a",{class:"header-anchor",href:"#requirements"},[n("span",null,"Requirements")])],-1),k=n("p",null,"The app consists of a movie explorer app with the following features:",-1),v=n("li",null,"Search for movies by title.",-1),m=n("li",null,"View the details of the selected movie.",-1),h=n("li",null,"The app requires the user to be logged in.",-1),b=n("li",null,"The app allows a new user to register.",-1),g=n("li",null,"The movie list screen allows to logout from the app.",-1),w=n("li",null,"The app remembers the logged in user after a restart.",-1),f={href:"https://movie-api-ybwl.koyeb.app/api-docs/",target:"_blank",rel:"noopener noreferrer"},_=n("ul",null,[n("li",null,[s("The "),n("strong",null,"/movies/search"),s(" endpoint requires to pass the token retrieved from endpoint "),n("strong",null,"/user/login"),s(" or "),n("strong",null,"user/register"),s(" in this header: "),n("code",null,"Authorization: Bearer \\(userResponse.token)")])],-1),y=n("li",null,"(Optional) The result of previous queries is locally cached.",-1),q=n("li",null,"(Optional) Add movie to local favorites ⭐️",-1),T={href:"https://www.hackingwithswift.com/quick-start/swiftui/how-to-add-and-remove-views-with-a-transition",target:"_blank",rel:"noopener noreferrer"},S=n("p",null,"A preview of the app can be seen here.",-1),x=n("iframe",{width:"720",height:"576",src:"https://www.youtube.com/embed/vh5AlaGK0Eo",title:"YouTube video player",frameborder:"0",allow:"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture",allowfullscreen:""},null,-1),I=e(`
There are many techniques to handle the flow from the login view to the movie list view. On of them is to rely on a logged state. The following gives an overview how it looks like.
structContentView:View{
+ @Statevar loggedIn:false
+
+ var body:someView{
+ if loggedIn {
+ MovieListView()
+ }else{
+ // The LoginView takes a callback that is called when the login succeeds
+ LoginView{ newLoggedIn in
+ loggedIn = newLoggedIn
+ }
+ }
+ }
+}
+
In the login view, use an enum to track the state of the login operation so that you can disable the login button when a request is running.
enumLoginState{
+ case neutral, loading, success, failure
+}
+structLoginView:View{
+ @Stateprivatevar loginState:LoginState=.neutral
+ // other code
+}
+
Do not use the Swift Playground app to run you app as it does not work well with SwiftUI + Swift Concurrency (async, await and Task). Instead, you can create an Xcode project of type Playground to combine the power of Xcode and the simplicity of Playground projects.
`,8),L={href:"https://github.com/Tunous/DebouncedOnChange",target:"_blank",rel:"noopener noreferrer"},V=n("li",null,[s("To generate the initial code for a preview, open a view and then use the Xcode feature "),n("em",null,"Editor -> Create preview")],-1),A=n("li",null,[s("The List view requires that you specify an "),n("code",null,"id"),s(" field "),n("code",null,"List(movies, id: \\.title)"),s(" or that the items conform to Identifiable protocol")],-1),C=n("li",null,[s("If you can't add SwiftPM packages from Xcode, add them by editing the "),n("em",null,"package.swift"),s(" file by hand. Here is an example below.")],-1),O=e(`
The /movies/search endpoint requires to pass the token retrieved from endpoint /user/login or user/register in this header: Authorization: Bearer \(userResponse.token)
(Optional) The result of previous queries is locally cached.
(Optional) Add movie to local favorites ⭐️
(Optional) Animate the transition between the login view and the movie list view (tutorialopen in new window).
There are many techniques to handle the flow from the login view to the movie list view. On of them is to rely on a logged state. The following gives an overview how it looks like.
structContentView:View{
+ @Statevar loggedIn:false
+
+ var body:someView{
+ if loggedIn {
+ MovieListView()
+ }else{
+ // The LoginView takes a callback that is called when the login succeeds
+ LoginView{ newLoggedIn in
+ loggedIn = newLoggedIn
+ }
+ }
+ }
+}
+
In the login view, use an enum to track the state of the login operation so that you can disable the login button when a request is running.
enumLoginState{
+ case neutral, loading, success, failure
+}
+structLoginView:View{
+ @Stateprivatevar loginState:LoginState=.neutral
+ // other code
+}
+
Do not use the Swift Playground app to run you app as it does not work well with SwiftUI + Swift Concurrency (async, await and Task). Instead, you can create an Xcode project of type Playground to combine the power of Xcode and the simplicity of Playground projects.
Persisting data locally consists of keeping app data after the app has been killed and the variables removed from memory. The persisted data offers many advantages. We can use it to show initial data when the app starts and waits for the first batch data to be fetched from the server. It can also be used to allow for offline app usage.
iOS isolates app data from other apps
For security reasons, each app is isolated from the rest of the apps. This is called sandboxing. This articleopen in new window shows the different ways that allow two or more apps to share their data
There are many ways to persist data in SwiftUI that we cover below.
It is a very simple key-value storage that persists data in a file. The API surface is very small and the developer does not need to manage the persisted file. This makes this technique very efficient for simple storage use cases. You can find a short guide hereopen in new window.
Here is sample code that shows how to persist and load data.
A more advanced and powerful technique is to manually load and persist a Codable into a file. This technique is useful if you want to store complex objects (such as the state or model) in a JSON file. There are two steps in this process, the first one consists of decoding / encoding the object from / into JSON using JSONDecoder().decode and JSONEncoder().encode. The second step consists of loading / saving the encoded data and we can think of two ways to achieve this. The first one consists of user defaults' dataForKey: to load the data and setObject:ForKey to persist it. Another one consists of creating and managing a file by the developer using file APIs such as fileHandle.availableData to load the data from a file and data.write to save it.
For storing data in a database or similar fashion, SQLite is available as a low level library. It is not recommended to use it unless there is a strong performance concern. Instead, it is recommended to use libraries specialized in data persistence. Some can be assimilated to an ORM library (Object Relational Mapper). The remainder of this section describes some of them.
Please be careful about the pricing of cloud storage
Sophisticated databases generally provide cloud storage to provide a complete offer. If you're interested in storing data in the cloud, please take some time to read the pricing page to avoid any bad surprises when your app runs in production.
Core Dataopen in new window is the official library to "Persist or cache data on a single device, or sync data to multiple devices with CloudKit". It existed since iOS 3 and Apple continuously updates it to keep it relevant. It also has the reputation of having a steep learning curve, but it remains famous among developers.
It works similarly as an ORM where classes are mapped into tables. Xcode provides a graphical editor that allows to specify the tables, the relations and generate the necessary code (in Swift or Objective-C).
Realmopen in new window is a high level alternative to SQLite. It can be seen as alternative to Core Data as they seem to provide a similar list of features. Most notably, the possibility to store data locally or in the cloud. The points where Realm wins is that the library seems simpler to learn and to use and that it is also available in Android.
As opposed to Realm and Core Data, which are local first databases, Firebase datastore is a cloud first database. This means that Firebase Datastore requires an internet connection to store and load the data. However, the library is simple to use and supports real time updates.
TIP
Firebase datastore is part of a bigger suite of service called Firebase. For example, we can Firebase App Distribution in Firebase, which is a service that allows to deploy and distribute apps without going the burden of using TestFlight.
iOS development consists of developing applications that can target mainly the iPhone and iPad but also macOS, iWatch and Apple TV. There are many ways to achieve this:
Using the official frameworks and tools provided by Apple
Using 3rd party frameworks and tools such as Capacitor, MAUI and Flutter
This training focuses on iOS development using the official tools and frameworks proposed by Apple. Our development stack will consist of the following items:
Programming language: Swift
UI Framework: SwiftUI
IDEs: Xcode and Swift Playgrounds
In addition to that, It is also possible to leverage the Swift language (without SwiftUI) in order to develop console apps and servers on Window, Linux, macOS.
The early days of iOS development used the Objective-C language, the UIKit UI Framework and -the good old- Xcode. This ecosystem was basic but quite powerful and allowed to develop amazing apps. The continuous updates from Apple improved the developer experience. For example, memory management became automatic (thanks to ARC) and the layout system became capable of adapting to different screen sizes.
In WWDC 2014, Apple announced the Swift language as an Open Source modern replacement to Objective-C. Following that, apple announced during the next WWDC SwiftUI as the replacement for UIKit.
swiftui
As of 2021, the majority of new iOS projects use Swift and SwiftUI with UIKit as a fallback for the UI aspects.
Swift is the official programming language for developing iOS, iPadOS, macOS, watchOS and AppleTV apps. It can also target other platforms such as Windows, Linux and Android.
In the this section, the terms argument and parameter are used interchangeably.
The declaration of functions in Swift has the following peculiarities:
Parameters are named and ordered. This means that when you call a function, you must specify the name of the arguments in the same order as the declaration.
A parameter can have different external and internal names by declaring it like this: externalName internalName: Type. The external name is also called an argument label.
You can make a parameter anonymous by setting this external name: _.
Arguments can have a default value. These are also called optional arguments.
Swift allows to use functions as first class items or citizens. This allows to store function references into variables, pass functions as arguments to other functions and return a function from a function. Here is a brief listing of the these features:
A function can be assigned to a variable, passed as a function parameter or returned from a function.
A function type can be expressed as follows: (typeOfParam1, typeOfParam2, etc) -> returnType.
The empty return type is Void.
We can use typealias to shorten writing long types.
Swift supports anonymous functions (also called lambda function) with the following syntax { argName1, argName2, etc. in // code }
In a nutshell, optionals is a compiler feature that allows you to avoid the infamous Null pointer exception or npe. The Swift compiler provides null safety and reports errors and warnings when we manipulate nullable (also called optional) values. Here is a list of null safety features provided by swift:
The name of null in iOS development
In Swift, the null value is called nil
All types are non optional by default. This means that we cannot assign nil to a variable or an argument. For example, this code fails var s: String = nil.
A type can be made optional by suffixing it with a ?. For example: var s: String? = nil.
You cannot call a method or a property of an optional type, unless you do one of those possibilities:
Use optional chaining with the ? suffix.
Provide a default value with the ?? operator.
Unwrap the optional so that it becomes non optional.
Force unwrap the optional using the ! suffix. This should never be used as it bypasses compiler checks.
Never unwrap with !
You must never force unwrap with the !. Use other unwrapping techniques instead. On of the rarest exceptions is with Interface builder's Outlets in UIKit @IBOutlet var label: UILabel!. Fortunately, since we are not using UIKit in this training, we will avoid this situation.
They are used a lot by swift developers to the point that there is a programming technique called Protocol oriented programming.
Here are some additional features:
Extensions allow to add functions and conform to additional protocols outside of the original class, struct or protocol declaration. This has many uses that simplify our code and here are some examples.
They can add methods to classes from any library that we can use.
They can define default implementations in protocols.
In Swift, structs have many similar features with classes. They support properties, methods, subscriptsopen in new window, initializers, extensions and conforming to protocols. The features that are only available in classes are as followsopen in new window:
Inheritance.
Type casting (enables you to check and interpret the type of a class instance at runtime).
Deinitializers.
Reference counting allows more than one reference to a class instance (similar to pointers but much less complex to use).
This feature seems advanced to understand but since it's used a lot in SwiftUI, let's explore a simple explanation and we'll provide some links to study it further.
In a base level, opaque types allow to return Protocols while keeping the concrete type information known by the compiler. It is enabled by prefixing the type with the some keyword.
Opaque types allow to keep the benefits of abstracting the code on a developer level while maintaining the performance and optimization benefits of concrete typing. In addition to that, they allow the compiler to better handle some cases such as Self or associated type requirements. Please note that explaining all the features that opaque types bring to the code is an advanced topic. For more information and details, please read the articles mentioned in the Sources and more reading section.
For this training, we'll assume that opaque help types the compiler perform better optimizations with protocols, are used in many places in SwiftUI and allow to improve our code in some cases. We'll show below a simple use case where we can define a method that returns an Equatable.
// Source: https://www.educative.io/answers/what-is-opaque-type-in-swift
+
+// create a function that returns some Equatable
+// The compiler fails is the return type is just "Equatable"
+funcmakeInteger()->someEquatable{
+ Int.random(in:0...10)
+}
+
+let firstInteger =makeInteger()
+let secondInteger =makeInteger()
+
+// this returns "false" because they are of the same concrete type else, Xcode will scream at us.
+print(firstInteger == secondInteger)
+
+funcmakeString()->someEquatable{
+ "A String"
+}
+let firstString =makeString()
+
+// Compiler error because the concrete type is not the same.
+print(firstInteger == firstString)
+
As surprising as it seems, Apple recommends using structs by default instead of classesopen in new window. More precisely, when we want to add a new data type, we should not assume that it should be a class by default and check if a structure is more relevant. Apple provides the following recommendations:
Use structures by default.
Use classes when you need Objective-C interoperability.
Use classes when you need to control the identity of the data you’re modeling.
Use structures along with protocols to adopt behavior by sharing implementations.
We note that structures are the default choice mostly because they are value types. This makes the code more predictable because changes cannot come from a parent call. Another advantage of structs is that they are more friendly with functional programming. We'll talk about functional programming in the next section.
Pure functions are functions that do not have side effects and will thus return always the same output given the same input. Swift allows to create pure functions but does not provide compile time guarantees that a function is pure.
Immutable objects can be created using classes or structs with constant properties (declared with let). As mentioned above, structs are recommended by default and here are other good reasonsopen in new window. One of the most notable ones is that since structs are passed around by value, thus they help us avoiding side effects.
Declarative programming can be easily explained as a way of programming that is centered around telling what to do and not how to do itopen in new window. This allows to obtain a clearer and more maintainable code than traditional imperative programming. For example, when we want to filter a table, a for loop is not declarative (we say imperative in this case) while the WHERE SQL syntax is considered declarative. Declarative programing is possible in Swift through chaining functions and passing functions as arguments. Indeed, as we have seen earlier, Swift has 1st class support for functions. In addition to that, we can find declarative APIs in the standard Swift library and in Swift UI. The latter will be explored in a different chapter. For now, let's illustrate with this codeopen in new window how to process a list of strings using only declarative APIs provided by Swift.
Swift has many more features and provides a rich standard library. We'll explore them as needed in the next sections. For now, let's create some UIs in the next chapter.
Swift supports writing concurrent code in a structured way.
Concurrency means that we execute multiple tasks at the same time. For example, update the UI while the app performs an HTTP request to the server.
In Swift, we can create concurrent Tasks with the Task, TaskGroup types.
Without Structured concurrency, we would use complex concepts to such as callbacks which make code less readable (have you lived the callback hellopen in new window ?).
We say that a code is structuredopen in new window when we use the well-know control flow structures :if/then/else, loops, functions, lexical scopes for variables.
Structured concurrency means that we write concurrent code using the usual control flow structures (as opposed to callback-based concurrent code)
In Swift is possible through the async and await keywords.
When we await a Task, the control flow will continue when it end without blocking the Task or TaskGroup on which it is launched.
A function that has uses the await keyword must be declared as async
To summarize async and await + Task and TaskGroup = Structured Concurrency
Continuations allow to convert callback code into async/await
// Reference: https://stackoverflow.com/a/24066317
+importPlaygroundSupport
+
+//Playground does not stop at the end of the code
+PlaygroundPage.current.needsIndefiniteExecution =true
+
+funcsampleFunc()async{
+ print("sampleFunc")
+ try?awaitTask.sleep(until:.now +.seconds(2))
+}
+
+Task{
+ awaitsampleFunc()
+ print("done")
+ // End the playground
+ PlaygroundPage.current.finishExecution()
+}
+
SwiftWasm Padopen in new window is an online editor that allows to write SwiftUI code and run it in the browser. It relies on the TokamakUIopen in new window framework which is SwiftUI-compatbile framework(or a re-implementation of SwiftUI) for the web.
SwiftWebUIopen in new window is another project that allows to run a server that renders SwiftUI to the browser. Note that it is considered as a toy project by its creator.
This training was introduction on Swift and SwiftUI. It just scratched the surface of developing for the Apple development. There are many things that we didn't explore such as the accessibility, hardware features such as geolocation and the technical aspects of the developer account (certificates, provisioning profiles, etc.).
To go further, it is advised to watch the videos from Apple's WWDCopen in new window (WorldWide Developer Conference - pronounced "dubdub dee cee"). There many other resources available online that you should pick and choose depending on the needs. Here are some of them:
Apple provides two official UI frameworks : UIKit and SwiftUI.
UIKit is the originally used framework for UI development. It relies on defining the UI in a separate file (storyboard or xib) and the behavior in a swift file. In 2019, Apple release the first version of SwiftUI.
The remainder of this training focuses on SwiftUI.
Another promising alternative to watch is compnerd's windows portopen in new window of UIKit and SwiftUI. So, if you can have a recent version Xcode running, this is be the best IDE for SwiftUI development.
As noted earlier, SwiftUI views are structs that conforms to the View protocol. This protocol defined a computed property that returns a View as an opaque type.
The body of the view has a VStack as its root element. A VStack is a container view that arrange its direct children vertically (on a column). The first child is a Text view and its second child is a Button.
The Text view chains calls to some methods that we call modifiers. They allow to do anything that we want to the view that called it and they return a new View instance. This means that we can apply another modifier to the result of a modifier and so on (this is called chaining). This allows modifiers to have a declarative syntax that makes the code easy to understand. SwiftUI provides built-in modifiers and allows us to create custom ones. Can you match all the modifiers used in the code and their effects ?
The button has no action, meaning that is does nothing on click and its content is defined as an HStack. An HStack is a container view that arrange its direct children horizontally (on a row). The stack contains an image and a button.
The view renders as illustrated by the image below.
@State: Single source of truth of a view and should not be shared with other views.
@Binding: allows to pass a reference of a state to a child view using $state.
@EnvironmentObject: Allows to globally share data between views. An @EnvironmentObject conforms to the ObservableObject protocol and its properties have the @Published property wrapper.
@ObservedObject: Allows to observe changes in an object that conforms to the ObservableObject protocol.
Apple provides a comprehensive SwiftUI tutorialopen in new window that covers most of the basic use cases such as creating views and handling inputs, animations and transitions.
Please cover these tutorials to get a good grasp of SwiftUI.
