主要用于項目中獲取驗證碼環節,參考了之前搜索的網絡資料,權作記錄.
TimerCountDown.h文件內:

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface TimerCountDown : NSObject

/**
 倒計時<獲取驗證碼>
 @param inButton 獲取驗證碼的點擊按鈕
 @param duration 倒計時時長
 */
+ (void)startCountDown:(UIButton *)inButton duration:(NSInteger)duration;
@end

TimerCountDowm.m 文件內:

#import "TimerCountDown.h"

@implementation TimerCountDown

+ (void)startCountDown:(UIButton *)inButton duration:(NSInteger)duration {
    
    __block NSInteger timeout = duration;
    
    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) {
            //倒計時結束
            dispatch_source_cancel(_timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                [inButton setTitle:@"獲取驗證碼" forState:UIControlStateNormal];
                [inButton setTitleColor:[UIColor colorWithRed:39/255.0 green:138/255.0 blue:228/255.0 alpha:1] forState:UIControlStateNormal];
                inButton.userInteractionEnabled = YES;
            });
        } else {
            //正在倒計時
            NSInteger seconds = timeout % 120;
            dispatch_async(dispatch_get_main_queue(), ^{
                [UIView animateWithDuration:1 animations:^{
                    [inButton setTitle:[NSString stringWithFormat:@"%ld秒后重發",seconds] forState:UIControlStateNormal];
                    [inButton setTitleColor:[UIColor lightGrayColor] forState:UIControlStateNormal];
                    inButton.userInteractionEnabled = NO;
                }];
            });
            timeout--;
        }
    });
    dispatch_resume(_timer);
}

@end

使用方式:
1.導入頭文件

#import "TimerCountDown.h"

2.在獲取驗證碼按鈕的點擊事件內:

- (IBAction)test:(id)sender {
    [TimerCountDown startCountDown:sender duration:10];
}