倒计时按钮

实现方式是通过Category

- (void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color {

    //倒计时时间
    __block NSInteger timeOut = timeLine;
    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);
    //每秒执行一次
    dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), 1.0 * NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler(_timer, ^{
        //倒计时结束，关闭
        if (timeOut <= 0) {
            dispatch_source_cancel(_timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                self.backgroundColor = mColor;
                [self setTitle:title forState:UIControlStateNormal];
                self.enabled = YES;
                self.userInteractionEnabled = YES;
            });
        } else {
            int seconds = timeOut % 60;
            NSString *timeStr = [NSString stringWithFormat:@"%0.2d", seconds];
            dispatch_async(dispatch_get_main_queue(), ^{
                self.backgroundColor = color;
                NSString *txt = [NSString stringWithFormat:subTitle,timeStr];
                self.titleLabel.text = txt;
                [self setTitle:txt forState:UIControlStateNormal];
                self.userInteractionEnabled = NO;
            });
            timeOut--;
        }
    });
    dispatch_resume(_timer);
}