GCD 定时器操作

var seconds = 10 //倒计时时间
        let queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
        let timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
        dispatch_source_set_timer(timer,dispatch_walltime(nil, 0),1 * NSEC_PER_SEC, 0); //每秒执行
        dispatch_source_set_event_handler(timer) { 
            if(seconds<=0){ //倒计时结束，关闭
                dispatch_source_cancel(timer);
                dispatch_async(dispatch_get_main_queue(), {
                    //设置界面的按钮显示 根据自己需求设置
                    btn.setTitleColor(UIColor.blackColor(), forState:.Normal)
                    btn.setTitle("获取验证码", forState:.Normal)
                    btn.titleLabel?.font = defaultFont14
                    btn.userInteractionEnabled = true
                    });
            }else{
                
                dispatch_async(dispatch_get_main_queue(), {
                    UIView.beginAnimations(nil, context: nil)
                    UIView.setAnimationDuration(1)
                })
                dispatch_async(dispatch_get_main_queue(), {
                    //设置界面的按钮显示 根据自己需求设置
                    UIView.beginAnimations(nil, context: nil)
                    UIView.setAnimationDuration(1)
                    btn.setTitleColor(UIColor.orangeColor(), forState:.Normal)
                    btn.setTitle("\(seconds)秒后重新发送", forState:.Normal)
                    btn.titleLabel?.font = UIFont.systemFontOfSize(11)
                    UIView.commitAnimations()
                    btn.userInteractionEnabled = false
                
                })
               seconds -= 1

        }
            
    }
    dispatch_resume(timer)