如何测试NSUserDefaults用户设置中是否存在BOOL？

I set a BOOL value in NSUserDefaults as follows.

我在NSUserDefaults中设置了一个BOOL值，如下所示。

[userDefaults setBool:NO forKey:@"theKeyOfMyBOOL"];

Somewhere else in my code, I want to perform some action if the key "theKeyOfMyBOOL" is not set in NSUserDefaults. How do I verify whether this key was set? If I do

在我的代码中的其他地方，如果未在NSUserDefaults中设置密钥“theKeyOfMyBOOL”，我想执行一些操作。如何验证此密钥是否已设置？如果我做

[userDefaults boolForKey:@"theKeyOfMyBOOL"];

then the value returned could be nil, which evaluates to false I believe, or the actual BOOL value of NO, which values to false.

那么返回的值可能是nil，我认为它的计算结果为false，或NO的实际BOOL值，其值为false。

However, I need to differentiate between these two values (as well as YES of course). How do I reliably do that?

但是，我需要区分这两个值（当然也是YES）。我如何可靠地做到这一点？

1 个解决方案

#1

[userDefaults boolForKey:@"theKeyOfMyBOOL"]; returns a BOOL, so either YES or NO (not nil).

[userDefaults boolForKey：@“theKeyOfMyBOOL”];返回BOOL，所以YES或NO（不是nil）。

Internally, it is stored as an NSNumber. So, if you call

在内部，它存储为NSNumber。所以，如果你打电话

[userDefaults objectForKey:@"theKeyOfMyBOOL"];

you will be given an NSNumber, if you have ever stored anything, or nil, if you have not.

如果你曾经存过任何东西，你将获得NSNumber，如果你没有，你将获得nil。

#1