iOS，倒計時獲取驗證碼效果

以下代碼出自 https://www.jianshu.com/p/786e882787b4
記錄一下

@implementation UIButton (CountDown)

/**
 倒計時

 @param timeLine 倒計時時間
 @param title 正常時顯示文字
 @param subTitle 倒計時時顯示的文字（不包含秒）
 @param countDoneBlock 倒計時結束時的Block
 @param isInteraction 是否希望倒計時時可交互
 */

- (void)countDownWithTime:(NSInteger)timeLine withTitle:(NSString *)title andCountDownTitle:(NSString *)subTitle countDoneBlock:(CountDoneBlock)countDoneBlock isInteraction:(BOOL)isInteraction{
    __block NSInteger timeout = timeLine; // 倒計時時間
    
    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); // 每秒執行
    
    dispatch_source_set_event_handler(_timer, ^{
        
        if(timeout<=0){ //倒計時結束，關閉
            
            dispatch_source_cancel(_timer);
            
            dispatch_async(dispatch_get_main_queue(), ^{
                
                if (countDoneBlock) {
                    countDoneBlock(self);
                }
                //設置界面的按鈕顯示 根據自己需求設置
                self.userInteractionEnabled = YES;
                [self setTitle:title forState:UIControlStateNormal];
                [self setTitleColor:[AXUtils colorWithString:kColor16_Theme] forState:UIControlStateNormal];
                self.titleLabel.font = [UIFont fontWithName:@"PingFangSC-Regular" size:14];
            });
            
        }else{
            
            //            int minutes = timeout / 60;
            
            int seconds = timeout % 60;
            
            NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];;
            if (seconds < 10) {
                strTime = [NSString stringWithFormat:@"%.1d", seconds];
            }
            
            dispatch_async(dispatch_get_main_queue(), ^{
                
                //設置界面的按鈕顯示 根據自己需求設置
                
//                NSLog(@"____%@",strTime);
                
                [self setTitle:[NSString stringWithFormat:@"%@s%@",strTime,subTitle] forState:UIControlStateNormal];
                [self setTitleColor:[AXUtils colorWithString:@"c1c1c1"] forState:UIControlStateNormal];
                self.titleLabel.font = [UIFont fontWithName:@"PingFangSC-Regular" size:12];
                
                self.userInteractionEnabled = isInteraction;
                
            });
            
            timeout--;
            
        }
        
    });
    
    dispatch_resume(_timer);
}

@end