buttonカウントダウン

            button.backgroundColor=[UIColor colorWithRed:96/255.0 green:96/255.0 blue:96/255.0 alpha:1];
            button.userInteractionEnabled = NO;
            __block int timeout = 59; // 
            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(), ^{
                        //   
                        [button setTitle:@" " forState:UIControlStateNormal];
                        button.userInteractionEnabled = YES;
                        button.backgroundColor=[UIColor orangeColor];
                    });
                }else{
                    //            int minutes = timeout / 60;
                    int seconds = timeout % 60;
                    NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];
                    dispatch_async(dispatch_get_main_queue(), ^{
                        //   
                        [button setTitle:[NSString stringWithFormat:@"%@ ",strTime] forState:UIControlStateNormal];
                        button.userInteractionEnabled = NO;
                    });
                    timeout--;
                }
            });
            dispatch_resume(_timer);