iOS: Using blocks as a variable

If you're into iOS programming and has a background on other programming languages like Java, Javascript, PHP, or Python, these languages have their own style of defining lambda or closures which you can assign to a specific variable and then call that variable as a method or function per se.

I just wanted to take notes on this so I might not forget, and well share this with you. Below is a snippet part of the game I wrote which looks like this,

1.    void (^playComeAndRead)(BOOL)  = ^(BOOL finished) {
2.        double delayInSeconds = 0.3;
3.        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
4.        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
5.            if (_audioPlayer) {
6.                _audioPlayer = nil;
7.            }
8.           
9.            audioString=@"Come And Read";
10.            audioURL = [[NSBundle mainBundle] URLForResource:audioString withExtension:@"mp3"];
11.            NSError *error;
12.            _audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:audioURL error:&error];
13.            [_audioPlayer play];
14.        });
15.    };
16.   
17.    for (UIView *subview in [self.view subviews]) {
18.        if (subview.tag != 0 && subview.tag !=102) {
19.            reMOVE
20.            isFound = YES;
21.            [UIView transitionWithView:self.view duration:1.580 options:UIViewAnimationOptionTransitionCurlUp
22.                    animations:^ {
23.                        [self.view addSubview:_readScrollView];
24.                    }
25.                    completion: playComeAndRead
26.            ];
27.        }
28.    }

As you can see, from line 1, I have called and used it on line 25.

If you have some variabled to be added inside a block (a closure), be sure to declare that this variable is under the scope of __block.

Example,

__block int x = 123; //

Some articles or sites are helpful to look at,
http://agilewarrior.wordpress.com/2012/05/11/how-to-pass-blocks-as-variables-in-objective-c/

but the best is to look at Apple's Developer Manual,
http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/Blocks/Articles/bxVariables.html