Make it possible to write Core Animation's animation code with blocks using timers.

NSObject + CATransactionSupport

@import QuartzCore;


@interface NSObject (CATransactionSupport)

- (NSTimer *)startTimerWithInterval:(NSTimeInterval)interval block:(void (^)(void))block;

- (void)startAnimationWithDuration:(NSTimeInterval)duration block:(void (^)(void))block;
- (void)startAnimationWithDuration:(NSTimeInterval)duration block:(void (^)(void))block completionHandler:(void (^)(void))completionHandler;

@end


@implementation NSObject (CATransactionSupport)

- (NSTimer *)startTimerWithInterval:(NSTimeInterval)interval block:(void (^)(void))block
{
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:interval
                                                      target:self
                                                    selector:@selector(__performBlockForTimer:)
                                                    userInfo:block
                                                     repeats:NO];
    return timer;
}

- (void)__performBlockForTimer:(NSTimer *)timer
{
    void (^block)(void) = timer.userInfo;
    block();
}

- (void)startAnimationWithDuration:(NSTimeInterval)duration
                             block:(void (^)(void))block
{
    [self startTimerWithInterval:0 block:^{
        [CATransaction begin];
        [CATransaction setAnimationDuration:duration];
        block();
        [CATransaction commit];
    }];
}

- (void)startAnimationWithDuration:(NSTimeInterval)duration
                             block:(void (^)(void))block
                 completionHandler:(void (^)(void))completionHandler
{
    [self startTimerWithInterval:0 block:^{
        [CATransaction begin];
        [CATransaction setAnimationDuration:duration];
        [CATransaction setCompletionBlock:completionHandler];
        block();
        [CATransaction commit];
    }];
}

@end