iOS中一句代码解决倒计时问题

最近工作比较忙，然后最近也在尝试着翻译一篇关于CALayer非常详解的一篇文章，文章还是比较好也比较长的，等整理完了再发布出来吧。所以也没啥多余的时间写些东西，就先来分享一下开发中的一些小Tips吧。

一、倒计时问题
在开发中经常遇到倒计时倒计时问题，写一个Button，然后各种判断各种状态，好多代码感觉很乱，下面就分享一下，一句话解决倒计时问题的例子（当然不是万能的，只适合大部分普通的倒计时^_）！
先看效果
http://upload-images.jianshu.io/upload_images/571495-92c1547f64ea24f6.gif?imageMogr2/auto-orient/strip

再看看我们的代码

 //
 // ViewController.m
 // HWCountdownDemo
 //
 // Created by HenryCheng on 16/1/4.
 // Copyright © 2016年 www.igancao.com. All rights reserved.
 //
 
 
import "ViewController.h"
 
 
import "UIButton+countDown.h"
 
 
@interface ViewController ()
 @property (weak, nonatomic) IBOutlet UIButton *countdownBtn;
 
 
@end
 
 
@implementation ViewController
 
 
 
  
(void)viewDidLoad {
 [super viewDidLoad];
 
 
 
 
}
 
 
 
  
(IBAction)countdownBtnClick:(UIButton *)sender {
 [_countdownBtn startWithTime:5 title:@"获取验证码" countDownTitle:@"s" mainColor:[UIColor colorWithRed:84/255.0 green:180/255.0 blue:98/255.0 alpha:1.0f] countColor:[UIColor lightGrayColor]];
 }
 
  
(void)didReceiveMemoryWarning {
 [super didReceiveMemoryWarning];
 // Dispose of any resources that can be recreated.
 }
 
 
 
 
@end
 

这里主要的就是xib拉了一个button然后连接了它的属性和方法，我们可以看到就调用了

[_countdownBtn startWithTime:5 title:@"获取验证码" countDownTitle:@"s" mainColor:[UIColor colorWithRed:84/255.0 green:180/255.0 blue:98/255.0 alpha:1.0f] countColor:[UIColor lightGrayColor]];}

这一句代码，就完成了倒计时功能。
这里我写了一个category，里面代码是这样的

 //
 // UIButton+countDown.m
 // LiquoriceDoctorProject
 //
 // Created by HenryCheng on 15/12/4.
 // Copyright © 2015年 iMac. All rights reserved.
 //
 
 
import "UIButton+countDown.h"
 
 
@implementation UIButton (countDown)
 
 
 
  
 
(void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color {
 
//倒计时时间
 __block NSInteger timeOut = timeLine;
 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);
 //每秒执行一次
 dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), 1.0 * NSEC_PER_SEC, 0);
 dispatch_source_set_event_handler(_timer, ^{
 
  //倒计时结束，关闭
  if (timeOut <= 0) {
      dispatch_source_cancel(_timer);
      dispatch_async(dispatch_get_main_queue(), ^{
          self.backgroundColor = mColor;
          [self setTitle:title forState:UIControlStateNormal];
          self.userInteractionEnabled = YES;
      });
  } else {
      int seconds = timeOut % 60;
      NSString *timeStr = [NSString stringWithFormat:@"%0.2d", seconds];
      dispatch_async(dispatch_get_main_queue(), ^{
          self.backgroundColor = color;
          [self setTitle:[NSString stringWithFormat:@"%@%@",timeStr,subTitle] forState:UIControlStateNormal];
          self.userInteractionEnabled = NO;
      });
      timeOut--;
  }
 
});
 dispatch_resume(_timer);
 }
 
 
 
 
 
@end
 

关于这个方法的定义

 //
 // UIButton+countDown.h
 // LiquoriceDoctorProject
 //
 // Created by HenryCheng on 15/12/4.
 // Copyright © 2015年 iMac. All rights reserved.
 //
 
 
import 
 
 
@interface UIButton (countDown)
 
 
/**
 
 
 
  
倒计时按钮
 
  
 
 
  
@param timeLine 倒计时总时间
 
  
@param title 还没倒计时的title
 
  
@param subTitle 倒计时中的子名字，如时、分
 
  
@param mColor 还没倒计时的颜色
 
  
@param color 倒计时中的颜色
 */
 
 
 
 
 
  
(void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color;
 
 
 
 
@end