1 GCD?

double delayInSeconds = 2.0;

//? 延時2秒執行返回

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));

dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

這里做想做的事情

});

2 NSTimer

[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(delayMethod) userInfo:nil repeats:NO];

此方式要求必須在主線程中執行，否則無效。

是一種非阻塞的執行方式，

可以通過NSTimer類的- (void)invalidate;取消執行

3 performSelector 方法

[self performSelector:@selector(delayMethod) withObject:nil afterDelay:1.0f];