- (void)viewDidLoad {

    [super viewDidLoad];

    dispatch_async(dispatch_get_global_queue(0, 0), ^{

        //1.创建定时器

        NSTimer *timer = [NSTimer timerWithTimeInterval:2.0 target:self selector:@selector(run) userInfo:nil repeats:YES];

        //2.将Timer添加到RunLoop中

        [[NSRunLoop currentRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];        

        //3.让RunLoop运行起来

        [[NSRunLoop currentRunLoop] run];//死循环，后面的代码不会执行

        NSLog(@"+++++++++");

    });

}

- (void)run {

    //耗时操作

    [NSThread sleepForTimeInterval:1.0];

    NSLog(@"-------- %@",[NSThread currentThread]);

}

- (void)viewDidLoad {

    [super viewDidLoad];

   [NSThread detachNewThreadSelector:@selector(time2) toTarget:self withObject:nil];

}

-(void)time2{

    //创建当前线程的RunLoop

    NSRunLoop *currentLoop = [NSRunLoop currentRunLoop];

    //该方法内部自动添加到RunLoop中，并且运行模式是默认模式

    [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(run) userInfo:nil repeats:YES];

    //开启RunLoop

    [currentLoop run];

}

- (void)run {

    //耗时操作

    [NSThread sleepForTimeInterval:1.0];

    NSLog(@"run ----- %@ ---- %@",[NSThread currentThread],[NSRunLoop currentRunLoop].currentMode);

}