NSTimer

1. block

示例代码：

@property (nonatomic, strong) NSTimer *timer;

// 1. 初始化定时器
self.timer = [NSTimer timerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
}];

// 2. 将定时器加入RunLoop
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];

// 3. 将定时器移出RunLoop
[self.timer invalidate];

引用关系图：

来源：https://blog.csdn.net/suma110/article/details/102755277