定时器

定时器在开发中经常使用的，下面说两种定时器的的实现。

1：使用 GCD实现 (防止按钮重复点击)

//计时器
-(void)startTime:(UIButton *)sender{
    
    __block int timeout = 60;
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), 1.0 * NSEC_PER_SEC,0);
    dispatch_source_set_event_handler(timer, ^{
        if (timeout < 0) {
            dispatch_source_cancel(timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                sender.userInteractionEnabled = YES;
                [sender setTitle:@"开启倒计时" forState:UIControlStateNormal];
            });
        }else{
            NSString *strTime = [NSString stringWithFormat:@"剩余时间：%.2d", timeout];
            dispatch_async(dispatch_get_main_queue(), ^{
                sender.userInteractionEnabled = NO;
                [sender setTitle:strTime forState:UIControlStateNormal];
            });
            timeout--;
        }
    });
    dispatch_resume(timer);
}

2：使用 RAC 实现 (防止按钮重复点击)

- (IBAction)start:(UIButton *)sender {
    sender.userInteractionEnabled = NO;
    [self Timer:sender];
}

-(void)Timer:(UIButton *)sender{
    static NSInteger seconds;
    seconds = 10;
//take :只去前11个信号，可按要求自己改其他的参数
    [[[RACSignal interval:1 onScheduler:[RACScheduler mainThreadScheduler]] take:11]
     subscribeNext:^(NSDate * date) {
         _timeLabel.text = [NSString stringWithFormat:@"%ld",seconds];
         seconds--;
         
         if (seconds < 0) {
             sender.userInteractionEnabled = YES;
             return ;
         }
    }];
    
    
}