发送短信成功后需要倒计时一段时间才能够再次发送，在此记录一个比较好的实现方法，如有什么问题欢迎指正.

1.申明一个全局定时器timer

dispatch_source_t _timer;

2.加载页面时候读取存储的时间戳time与当前时间戳比较小于60秒计时

//和当前时间戳比较//取当前时间于保存的时间比较，大于60秒继续计时

NSDate *date = [NSDate date];

NSInteger timeFlag = [self timeIntergerWithDate:date];

NSInteger time = timeFlag;

time =  [[NSUserDefaults standardUserDefaults] integerForKey:@"timecount"];

//两者比较，若小于60秒开始计时

if (timeFlag-time < 60) {

[self openCountdownWithTimeCount:60-(timeFlag - time)];

}

3.点击获取验证码按钮时保存时间

NSDate *date = [NSDate date];

NSInteger timeFlag = [self timeIntergerWithDate:date];

[[NSUserDefaults standardUserDefaults] setInteger:timeFlag forKey:@"timecount"];

4.页面关闭时销毁定时器

- (void)viewWillDisappear:(BOOL)animated{

[super viewWillDisappear:animated];

if (_timer) {

dispatch_source_cancel(_timer);

}

}

附1.倒计时方法

// 开启倒计时效果

-(void)openCountdownWithTimeCount:(NSInteger)timeCount{

__block NSInteger time = timeCount; //倒计时时间

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

_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); //每秒执行

dispatch_source_set_event_handler(_timer, ^{

if(time <= 0){ //倒计时结束，关闭

dispatch_source_cancel(_timer);

dispatch_async(dispatch_get_main_queue(), ^{

//设置按钮的样式

[self.authCodeBtn setTitle:@"获取验证码" forState:UIControlStateNormal];

self.authCodeBtn.backgroundColor = [UIColor redColor];

self.authCodeBtn.enabled = YES;

});

}else{

int seconds = time % 60;

dispatch_async(dispatch_get_main_queue(), ^{

//设置按钮显示读秒效果

[self.authCodeBtn setTitle:[NSString stringWithFormat:@"%.2d", seconds] forState:UIControlStateNormal];

self.authCodeBtn.backgroundColor = [UIColor lightGrayColor];

self.authCodeBtn.enabled = NO;

});

time--;

}

});

dispatch_resume(_timer);

}

附2：时间转换时间戳

+ (long)timeIntergerWithDate:(NSDate *)date{

long firstStamp = [date timeIntervalSince1970];

return firstStamp;

}