很多应用在修改密码或者是更改个人信息时，需要用户输入手机验证码，其间有个等待过程，一般为60秒，等待结束后可以重新点击按钮获取新的验证码，在页面来回跳转之后又可以重新计时，简要做以下整理：

在.h文件中声明计时器

@interface LinViewController : UIViewController

@property (strong, nonatomic) UIButton * button;

@property (strong, nonatomic) NSTimer * timer;

@end

//当页面有跳转的操作的时间需要调用[self.timer invalidate]，使计时器停止，否则会造成时间连续走动

static int myTime;

- (void)viewWillAppear:(BOOL)animated
{
    [self.timer invalidate];
    self.timer= [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(changeButtonName) userInfo:nil repeats:YES];
    
    self.button.enabled = NO;
    self.button.titleLabel.text = @"10秒后重新获取";
    myTime = 10;
}

- (void)viewWillDisappear:(BOOL)animated
{
    [self.timer invalidate];
}

- (void)changeButtonName
{
    if (myTime > 0) {
        self.button.enabled = NO;
        myTime--;
        NSString * string = [NSString stringWithFormat:@"%d秒后重新获取",myTime];
        NSLog(@"%@===",string);
        self.button.titleLabel.text = string;
    }else
    {
        [self.timer invalidate];
        self.button.enabled = YES;
    }
}

- (void)addButtonAction
{
    [self.timer invalidate];
    [self viewWillAppear:YES];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    self.button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [self.button setFrame:CGRectMake(90, 90, 200, 30)];
    [self.button setTitle:@"重新获取验证码" forState:UIControlStateNormal];
    [self.button addTarget:self action:@selector(addButtonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.button];
}