Implemented createPost resolver

lib/cdk-typescript-stack.ts

@@ -3,13 +3,22 @@ import * as appsync from '@aws-cdk/aws-appsync-alpha';
 
 import { Stack, StackProps, CfnOutput } from 'aws-cdk-lib';
 import { Construct } from 'constructs';
-import { aws_cognito as cognito } from 'aws-cdk-lib';
+import { 
+  aws_cognito as cognito, 
+  aws_dynamodb as dynamodb,
+  aws_lambda as lambda 
+} from 'aws-cdk-lib';
 
 
 export class CdkTypescriptStack extends Stack {
   constructor(scope: Construct, id: string, props?: StackProps) {
     super(scope, id, props);
 
+    const postsTable = new dynamodb.Table(this, 'PostsTable', {
+      partitionKey: {name: 'id', type: dynamodb.AttributeType.STRING},
+      replicationRegions: ['us-east-1']
+    });
+
     const userPool = new cognito.UserPool(this, 'CdkAuth', {
       userPoolName: 'CdkAuth',
       selfSignUpEnabled: true,
@@ -44,6 +53,16 @@ export class CdkTypescriptStack extends Stack {
       xrayEnabled: true,
     });
 
+    const postsDS = api.addDynamoDbDataSource('postsTable', postsTable);
+
+    // create post
+    postsDS.createResolver({
+      typeName: 'Mutation',
+      fieldName: 'createPost',
+      requestMappingTemplate: appsync.MappingTemplate.fromFile('mapping-template/Mutation.createPost.request.vtl'),
+      responseMappingTemplate: appsync.MappingTemplate.dynamoDbResultItem()
+    });
+
     new CfnOutput(this, 'GraphQL_URL', { value: api.graphqlUrl });
 
   }

mapping-template/Mutation.createPost.request.vtl

@@ -0,0 +1,15 @@
+{
+  "version" : "2018-05-29",
+  "operation" : "PutItem",
+  "key": {
+    "id": $util.dynamodb.toDynamoDBJson($util.autoUlid())
+  },
+  "attributeValues" : {
+    "title": $util.dynamodb.toDynamoDBJson($context.arguments.title),
+    "text": $util.dynamodb.toDynamoDBJson($context.arguments.text),
+    "createdAt": $util.dynamodb.toDynamoDBJson($util.time.nowISO8601()),
+  },
+  "condition" : {
+    "expression" : "attribute_not_exists(id)"
+  },
+}