iOS开发中延迟执行的三种方法

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第一种: performSelector

[self performSelector:@selector(run) withObject:nil afterDelay:2.0];

第二种: NSTimer

[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(run) userInfo:nil repeats:YES];

第三种: GCD

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [self run];
    });

注 : run是方法