IOS实现验证码倒计时功能（一）

@interface IDCountDownButton : UIButton
/** 验证码倒计时的时长 */
@property (nonatomic, assign) NSInteger durationOfCountDown;
@end

@interface IDCountDownButton ()
/** 保存倒计时按钮的非倒计时状态的title */
@property (nonatomic, copy) NSString *originalTitle;
/** 保存倒计时的时长 */
@property (nonatomic, assign) NSInteger tempDurationOfCountDown;
/** 定时器对象 */
@property (nonatomic, strong) NSTimer *countDownTimer;
@end

- (void)setTitle:(NSString *)title forState:(UIControlState)state {
 [super setTitle:title forState:state];
 // 倒计时过程中title的改变不更新originalTitle
 if (self.tempDurationOfCountDown == self.durationOfCountDown) {
 self.originalTitle = title;
 }
}

- (void)setDurationOfCountDown:(NSInteger)durationOfCountDown {
 _durationOfCountDown = durationOfCountDown;
 self.tempDurationOfCountDown = _durationOfCountDown;
}

- (instancetype)initWithFrame:(CGRect)frame {
 if (self = [super initWithFrame:frame]) {
 // 设置默认的倒计时时长为60秒
 self.durationOfCountDown = 60;
 // 设置button的默认标题为“获取验证码”
 [self setTitle:@"获取验证码" forState:UIControlStateNormal];
 }
 return self;
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
 if (self = [super initWithCoder:aDecoder]) {
 // 设置默认的倒计时时长为60秒
 self.durationOfCountDown = 60;
 // 设置button的默认标题为“获取验证码”
 [self setTitle:@"获取验证码" forState:UIControlStateNormal];
 }
 return self;
}

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
 // 若正在倒计时，不响应点击事件
 if (self.tempDurationOfCountDown != self.durationOfCountDown) {
 return NO;
 }
 // 若未开始倒计时，响应并传递点击事件，开始倒计时
 [self startCountDown];
 return [super beginTrackingWithTouch:touch withEvent:event];
}

- (void)startCountDown {
 // 创建定时器
 self.countDownTimer = [NSTimer timerWithTimeInterval:1 target:self selector:@selector(updateIDCountDownButtonTitle) userInfo:nil repeats:YES];
 // 将定时器添加到当前的RunLoop中（自动开启定时器）
 [[NSRunLoop currentRunLoop] addTimer:self.countDownTimer forMode:NSRunLoopCommonModes];
}

- (void)updateIDCountDownButtonTitle {
 if (self.tempDurationOfCountDown == 0) {
 // 设置IDCountDownButton的title为开始倒计时前的title
 [self setTitle:self.originalTitle forState:UIControlStateNormal];
 // 恢复IDCountDownButton开始倒计时的能力
 self.tempDurationOfCountDown = self.durationOfCountDown;
 [self.countDownTimer invalidate];
 } else {
 // 设置IDCountDownButton的title为当前倒计时剩余的时间
 [self setTitle:[NSString stringWithFormat:@"%zd秒", self.tempDurationOfCountDown--] forState:UIControlStateNormal];
 }
}

- (void)dealloc {
 [self.countDownTimer invalidate];
}

@interface ViewController ()
/** 验证码倒计时的button */
@property (nonatomic, strong) IDCountDownButton *vertificationCodeIDCountDownButton;
@end

- (void)viewDidLoad {
 [super viewDidLoad];
 // 创建vertificationCodeIDCountDownButton
 self.vertificationCodeIDCountDownButton = [[IDCountDownButton alloc] initWithFrame:CGRectMake(160, 204, 120, 44)];
 // 添加点击事件
 [self.vertificationCodeIDCountDownButton addTarget:self action:@selector(vertificationCodeIDCountDownButtonClick:) forControlEvents:UIControlEventTouchUpInside];
 // 设置标题相关属性
 [self.vertificationCodeIDCountDownButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
 [self.vertificationCodeIDCountDownButton setTitle:@"获取验证码" forState:UIControlStateNormal];
 // 设置背景图片
 [self.vertificationCodeIDCountDownButton setBackgroundImage:[UIImage imageNamed:@"redButton"] forState:UIControlStateNormal];
 // 设置倒计时时长
 self.vertificationCodeIDCountDownButton.durationOfCountDown = 10;
 // 将vertificationCodeIDCountDownButton添加的控制器的view中
 [self.view addSubview:self.vertificationCodeIDCountDownButton];
}

- (void)vertificationCodeIDCountDownButtonClick:(UIButton *)button {
 // TODO：调用服务器接口，获取验证码
}