【IOS 入门学习】延迟3秒执行Delay方法

[self performSelector:@selector(Delay) withObject:nil afterDelay:3.0f];

- (void)Delay {
 NSLog(@"执行"); 
}

[NSTimer scheduledTimerWithTimeInterval:3.0f target:self selector:@selector(Delay) userInfo:nil repeats:NO];

- (void)Delay {
 NSLog(@"执行"); 
}

[NSThread sleepForTimeInterval:3.0f];
[self Delay];

- (void)Delay {
 NSLog(@"执行"); 
}

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC));
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        [self Delay];
    });

- (void)Delay {
 NSLog(@"执行"); 
}