Cocoa - 关于NSUserDefaults的通知值的变化？ [英] Cocoa - Notification on NSUserDefaults value change?

问题描述

假设我有一个键MyPreference，通过NSUserDefaults存储相应的值。

Let's say I have a key @"MyPreference", with a corresponding value stored through NSUserDefaults.

当值被修改时，有没有办法被通知？

Is there a way to be Notified when the value is modified?

还是可以通过绑定完成？ （但是，这种情况下，我希望我的对象被通知这个更改，以便我可以执行其他任务。）

Or could it be done through bindings? (But this case, instead of binding the value to a UI element, I wish my object to be notified of the change, so that I can perform other tasks.)

我知道NSUserDefaultsDidChangeNotification可以被观察，但这似乎是一个全有或全无的方法，并且似乎没有一个机制来获得被修改的特定键值对。 （随意更正。）

I am aware that NSUserDefaultsDidChangeNotification can be Observed, but this appears to be a all-or-nothing approach, and there does not appear to be a mechanism there to get at the specific key-value-pair that was modified. (Feel free to correct.)

推荐答案

花一整天寻找答案，只有在提出问题10分钟后才能找到答案...

Spent all day looking for the answer, only to find it 10 minutes after asking the question...

通过Key-Value-Observing跨解决方案：

Came across a solution through Key-Value-Observing:

[[NSUserDefaultsController sharedUserDefaultsController] addObserver:self
    forKeyPath:@"values.MyPreference"
    options:NSKeyValueObservingOptionNew
    context:NULL];

或者，更简单的方法是下面的注释：

Or, more simply (per comment below):

[[NSUserDefaults standardUserDefaults] addObserver:self
                                        forKeyPath:@"MyPreference"
                                           options:NSKeyValueObservingOptionNew
                                           context:NULL];

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