替代延迟功能

Question

我使用以下代码来延迟更改文本：

int64_t delayInSeconds = 0.6;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
     label.text = %"ye";}

我无法取消此功能，因此如果我通过单击“返回”关闭我的viewController并立即再次打开它，该功能将更改文本。我该如何重写以允许取消？

Answer 1

self.timer = [NSTimer scheduledTimerWithTimeInterval:delayInSeconds
                                              target:self
                                            selector:@selector(updateLabel)
                                            userInfo:nil
                                             repeats:NO];


- (void)updateLabel
{
   self.label.text = %"ye";
}

并在viewWillDisapear:

中

[self.timer invalidate];

Answer 2

self.cancelled = NO; // cancelled is a BOOL property

int64_t delayInSeconds = 0.6;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    if (!self.cancelled) {
        label.text = %"ye";
    }
}

...

// When back is tapped
self.cancelled = YES;