iOS 8.2 [NSUserDefaults standardUserDefaults]返回nil [英] iOS 8.2 [NSUserDefaults standardUserDefaults] returning nil

问题描述

我在iOS 8.2中遇到一个奇怪的问题，其中[NSUserDefaults standardUserDefaults]在iPhone上返回nil。这种相同的逻辑未曾在所有以前版本的iOS上发挥过作用。我有一个通用应用程序有两个不同的settings.plist一个用于iPad，另一个用于iPhone列表如下;

I am encountering a strange issue in iOS 8.2 where [NSUserDefaults standardUserDefaults] is returning nil on iPhone. This same logic untouched has worked on all previous releases of iOS. I have a universal app which has two different settings.plist one for iPad and the other for iPhone list as follows;

Settings.bundle-
    -Root.plist
    -Root~iphone.plist

安装在设备上的正确设置窗格显示，用户可以输入给定字段的相应值。虽然在运行时我的应用程序[NSUserDefaults standardUserDefalts]返回一个nil对象。

When installed on devices the correct settings pane displays and the user can input the appropriate values for the given fields. Though in my app at runtime [NSUserDefaults standardUserDefalts] returns a nil object.

我可能做错了什么？ Apple是否改变了预期的8.2？

What might I be doing wrong? Has Apple changed what is expected in 8.2?

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

无论在系统设置中设置了什么首选项，userDefaults始终为nil。

userDefaults is always nil no matter what preferences are set in system settings.

推荐答案

您是否将字典设置为Settings.bundle / Root.plist？

Did you set the dictionary to use as "Settings.bundle/Root.plist"?

// Register the preference defaults from file "Settings.bundle/Root.plist"
NSDictionary *dictionary = [NSDictionary dictionaryWithContentsOfFile:
                            [[NSBundle mainBundle] pathForResource:@"Settings.bundle/Root"
                                                            ofType:@"plist"]];
[[NSUserDefaults standardUserDefaults] registerDefaults:dictionary];

此后 [NSUserDefaults standardUserDefaults] 不再是nil。

在我的例子中， [NSUserDefaults standardUserDefaults] 使用的字典在调试器中如下所示：

In my case, the dictionary used by [NSUserDefaults standardUserDefaults] looks like this in the debugger:

    {
        PreferenceSpecifiers =     (
                    {
                DefaultValue = 1;
                Key = sortByDistance;
                Title = "Sortiere nach Entfernung";
                Type = PSToggleSwitchSpecifier;
            }
        );
        StringsTable = Root;
    }

要访问首选项，我写了一个小方法：

To access the preferences I've written a tiny method:

- (id) preferenceValueForKey: (NSString *)key {
    NSArray *preferences = [[NSUserDefaults standardUserDefaults] arrayForKey:@"PreferenceSpecifiers"];
    NSUInteger index = [preferences indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
        return [[obj valueForKey:@"Key"] isEqualToString:key];
    }];
    return [preferences[index] valueForKey:@"DefaultValue"];
}

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