iOS 定时任务

• 方法1 performSelector

// 2.0s后自动调用self的test方法
[self performSelector:@selector(test) withObject:nil afterDelay:2.0];

• 方法2 GCD

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    // 2.0s后自动执行这个block里面的代码
    self.view.backgroundColor = [UIColor blueColor];
});

• 方法3 NSTimer

// 2.0s后自动调用self的test方法
[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(test) userInfo:nil repeats:NO];