IOS development-delayed execution

Sometimes, if you want to run a piece of code after a certain period of time, you need to use delayed execution.

There are several common methods:

1. The most direct method is performSelector: withObject: afterDelay: the disadvantage of this method: Write a method for the latency each time.

    [self performSelector:@selector(scale_2) withObject:nil afterDelay:0.5f];

-(void)scale_2{    UIImageView *round_2 = [[UIImageView alloc]initWithFrame:CGRectMake(105, 210, 20, 20)];    round_2.image = [UIImage imageNamed:@"round_"];    [splashView addSubview:round_2];    [self setAnimation:round_2];}

2. Use category and use BOLCK to execute

@implementation NSObject (PerformBlockAfterDelay)- (void)performBlock:(void (^)(void))block          afterDelay:(NSTimeInterval)delay{    block = [[block copy] autorelease];    [self performSelector:@selector(fireBlockAfterDelay:)               withObject:block               afterDelay:delay];}- (void)fireBlockAfterDelay:(void (^)(void))block {    block();}@end

3. Use GCD [Code] c #/cpp/oc code:

void RunBlockAfterDelay(NSTimeInterval delay, void (^block)(void)){    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC*delay),      dispatch_get_current_queue(), block);}

Poolo: note that the dispatch_getcurrent_queue () method in the figure has been kill in ios6. Now the first parameter of dispatch_get_global_queue (DISPATCH_QUEUE_PRIORITY_HIGH, 0) is priority, the second parameter is 0 or nil if you want to operate on the interface, use dispatch_get_main_queue (); reference: http://www.cnblogs.com/guwandong/archive/2012/08/08/2626211.html 4. this may not be a good method. Use the [Code] c #/cpp/oc code of the completion parameter of animation:

[UIView animateWithDuration:0.0 delay:5.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{} completion:^(BOOL finished) {    //do stuff here}];

5. Use NSOperationQueue to run in the next main loop of the application: [Code] c #/cpp/oc code:

1	[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];

This is equivalent to calling mongomselector: with afterDelay of 0.0f.

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