倒计时-UIButton-GCD-Block

//倒计时时间

__block int timeout= 2; 

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); //每秒执行

dispatch_source_set_event_handler(_timer, ^{

if(timeout<=0){ //倒计时结束，关闭

dispatch_source_cancel(_timer);

dispatch_async(dispatch_get_main_queue(), ^{

//倒计时结束，开始设置操作

aButton.userInteractionEnabled = YES;

});

}else{

//            int minutes = timeout / 60;

//            int seconds = timeout % 60;

//            NSString *strTime = [NSString stringWithFormat:@"%d分%.2d秒后重新获取验证码",minutes, seconds];

dispatch_async(dispatch_get_main_queue(), ^{

//开始倒计时，设置倒计时显示

aButton.userInteractionEnabled = NO;

});

timeout--;

}

});

dispatch_resume(_timer);