RunLoop（基本操作）

-(void)runTimerInThread
{
    //NSAutoreleasePool,没的用
    [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(doSth:) userInfo:self repeats:YES];
    
    //1.以上方法自动把NSTimer添加到RunLoop里面
    
    NSTimer* timer=[NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(doSth:) userInfo:self repeats:YES];
    
    //2.以上方法不会自动NSTimer添加到RunLoop里面
    [[NSRunLoop currentRunLoop]addTimer:timer forMode:NSDefaultRunLoopMode];
    //要手动加入runLoop,额额,类方法就写入了 addTimer:timer forMode:NSDefaultRunLoopMode;
    
    
    [[NSRunLoop currentRunLoop]run];
    //这很重要,把定时器的线程加入运行回环runloop才会使线程处于活跃状态

}

 [self performSelectorInBackground:@selector(runTimerInThread) withObject:nil];