__block int time = ;

         __block UIButton *verifybutton = _GetverificationBtn;

         verifybutton.enabled = NO;

         dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, );

         dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, , ,queue);

         dispatch_source_set_timer(_timer,dispatch_walltime(NULL, ),1.0*NSEC_PER_SEC, ); //每秒执行

         dispatch_source_set_event_handler(_timer, ^{

             if(time<=){ //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

                     [verifybutton setTitle:@"获取验证码" forState:UIControlStateNormal];

                     verifybutton.enabled = YES;

                 });

             }else{

                 dispatch_async(dispatch_get_main_queue(), ^{

                     //设置界面的按钮显示 根据自己需求设置

                     verifybutton.backgroundColor = [UIColor grayColor];

                     NSString *strTime = [NSString stringWithFormat:@"获取验证码(%d)",time];

                     [verifybutton setTitle:strTime forState:UIControlStateNormal];

                     verifybutton.titleLabel.textColor = [UIColor whiteColor];

                 });

                 time--;

             }

         });

         dispatch_resume(_timer);