NSTimer+AbsoluteFireDate.m

//
//  NSTimer+AbsoluteFireDate.m
//
//  Created by Adam Ernst on 11/26/10.
//  Copyright 2010 cosmicsoft. All rights reserved.
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.

#import "NSTimer+AbsoluteFireDate.h"


@interface NSTimerAbsoluteFireDateTracker : NSObject {
	NSMutableArray *timers;
}
+ (NSTimerAbsoluteFireDateTracker *)sharedTracker;
- (void)trackTimer:(NSTimer *)timer;
@end


@implementation NSTimer (AbsoluteFireDate)

- (id)initWithAbsoluteFireDate:(NSDate *)date target:(id)target selector:(SEL)aSelector userInfo:(id)userInfo {
	NSTimer *timer = [self initWithFireDate:date interval:0.0 target:target selector:aSelector userInfo:userInfo repeats:NO];
	[[NSTimerAbsoluteFireDateTracker sharedTracker] trackTimer:timer];
	return timer;
}

@end


@implementation NSTimerAbsoluteFireDateTracker

- (id)init {
	if (self = [super init]) {
		timers = [[NSMutableArray alloc] init];
		
		[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkTimers:) name:UIApplicationDidBecomeActiveNotification object:nil];
		if (&UIApplicationWillEnterForegroundNotification != NULL) {
			[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkTimers:) name:UIApplicationWillEnterForegroundNotification object:nil];
		}
	}
	return self;
}

- (void)dealloc {
	if (&UIApplicationWillEnterForegroundNotification != NULL) {
		[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillEnterForegroundNotification object:nil];
	}
	[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
	[timers release];
	[super dealloc];
}

static NSTimerAbsoluteFireDateTracker *sharedTracker;
+ (NSTimerAbsoluteFireDateTracker *)sharedTracker {
	if (sharedTracker == nil) {
		sharedTracker = [[NSTimerAbsoluteFireDateTracker alloc] init];
	}
	return sharedTracker;
}

- (void)trackTimer:(NSTimer *)timer {
	[timers addObject:timer];
}

- (void)checkTimers:(NSNotification *)notification {
	NSMutableArray *timersToRemove = [NSMutableArray array];
	// The timers array might be mutated if a fired timer
	// in turn creates an absolute-fire-date timer of its own.
	// Make a copy to avoid this problem.
	NSArray *currentTimers = [timers copy];
	
	for (NSTimer *timer in currentTimers) {
		if ([timer isValid]) {
			if ([[NSDate date] timeIntervalSinceDate:[timer fireDate]] > 0.0) {
				[timer fire];
			} else {
				[timer setFireDate:[timer fireDate]];
			}
		}
		
		if (![timer isValid]) {
			[timersToRemove addObject:timer];
		}
	}
	
	[currentTimers release];
	
	[timers removeObjectsInArray:timersToRemove];
}

@end