iOS 延时执行

1、
[self performSelector:@selector(removeAllSceneArrObjects) withObject:nil afterDelay:1.5f];

- (void)removeAllSceneArrObjects {
    NSLog(@"\n== 删除所有场景 OK");
}


2、GCD
double delayInSeconds = 2.0;   // 延时2秒执行返回
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW,
                                            (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void) {

});


3、NSTimer
// 是一种非阻塞的执行方式
// 可以通过 NSTimer 类的 - (void)invalidate; 取消执行
dispatch_async(dispatch_get_main_queue(), ^{
    // 此方式要求必须在主线程中执行, 否则无效
    [NSTimer scheduledTimerWithTimeInterval:1.0f
                                     target:self
                                   selector:@selector(delayMethod)
                                   userInfo:nil
                                    repeats:NO];
});

// ==================================================
@property (nonatomic, strong) NSTimer *timer;

#pragma mark - 定时器控制
- (void)startTimer {
    // 创建一个定时器  自动启动
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.5
                                                  target:self
                                                selector:@selector(nextPage)
                                                userInfo:nil
                                                 repeats:YES];
    

    self.timer = [NSTimer timerWithTimeInterval:1.5
                                         target:self
                                       selector:@selector(nextPage)
                                       userInfo:nil
                                        repeats:YES];
    // 启动
    [self.timer fire];
    
    [[NSRunLoop mainRunLoop] addTimer:self.timer
                              forMode:NSRunLoopCommonModes];
}

- (void)stopTimer {
    [self.timer invalidate];
    self.timer = nil; //释放内存
}