观察值更改为NSUserDefaults项 [英] Observing value changes to an NSUserDefaults key

问题描述

我对保存在NSUserdefaults中的特定键的值更改感兴趣.但是，我所拥有的对我不起作用. watchValueForKeyPath不会被触发.

I'm interested in the value change of a particular key which I keep in NSUserdefaults. However, what I have is not working for me. observeValueForKeyPath does not get triggered.

更新:我想我已经发现了问题.如果我使用字符串，则将其触发，而不是使用已定义的常量.

Update: I think I've discovered the issue. Rather than using a defined constant, if I use a string then it gets fired.

[[NSUserDefaults standardUserDefaults] addObserver:self forKeyPath:kSomethingInteresting options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld) context:nil];


}

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {

 NSLog(@"Defaults changed, %@.%@", object, keyPath);

 if ((object == [NSUserDefaults standardUserDefaults]) && [keyPath isEqualToString:kSomethingInteresting]) {
  NSLog(@"kSomethingInteresting changed in defaults");
 }
}

不太理想，但是如果我在addOberver行之前加上:

Not ideal but if I precede the addOberver line with:

NSString* keyToObserve = kSomethingInteresting;

然后在addObserver行中使用它，然后就可以了.看起来有点古怪?

And use that in the addObserver line then that works. Seems a bit fiddly?

推荐答案

因此，在这种情况下以及在需要观察用户默认值的所有情况下，我将放弃使用已定义的常量.真可惜，我喜欢在整个过程中使用它们作为键名.

So I'm going to scrap the use of a defined constant in this instance and in all instances where I need to observe something in userdefaults. Shame, as I like using them for key names throughout.

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