ios 简单的倒计时验证码数秒过程实现

 timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerFireMethod:) userInfo:nil repeats:YES];

//倒计时方法验证码实现倒计时60秒，60秒后按钮变换开始的样子
-(void)timerFireMethod:(NSTimer *)theTimer {
    if (seconds == 1) {
        [theTimer invalidate];
        seconds = 60;
        [validCodeBtn_ setTitle:@"获取验证码" forState: UIControlStateNormal];
        [validCodeBtn_ setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [validCodeBtn_ setEnabled:YES];
    }else{
        seconds--;
        NSString *title = [NSString stringWithFormat:MSG_DYNAMIC_CODE_WAIT,seconds];
        [validCodeBtn_ setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
        [validCodeBtn_ setEnabled:NO];
        [validCodeBtn_ setTitle:title forState:UIControlStateNormal];
    }
}
//如果登陆成功，停止验证码的倒数，
- (void)releaseTImer {
    if (timer) {
        if ([timer respondsToSelector:@selector(isValid)]) {
            if ([timer isValid]) {
                [timer invalidate];
                seconds = 60;
            }
        }
    }
}