self.time=[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(randomName:) userInfo:nil repeats:YES];
实现NSTimer里的方法
-(void)randomName:(id)sender{
self.a=arc4random()%12;
self.label.text=self.arr[self.a];
}
让NSTimer停下来的方法
- (void)invalidate;
随机点名
[self.time invalidate];