nsuserdefault的键值设置如何删除？

Question

I have already tried to delete all the key-values pair when the app starts and again when i check keys these keys are saved in NSUserDefault. I have these preferences stored.

NSArray *keys = [[[NSUserDefaults standardUserDefaults] dictionaryRepresentation] allKeys];
NSLog(@"all keys %@", keys);


keys (
    NSLanguages,
    AppleITunesStoreItemKinds,
    AppleLocale,
    AppleLanguages,
    NSInterfaceStyle
)

When I store new dynamic values to the NSUserDefaults, I want to select all the keys except these preferences.

Please help me with this problem.

Thanks in advance

Answer 1

Don't do what you're trying to do. Don't tamper with any of the keys added by Apple. Keep your own set of keys (preferably with prefixes on the names) and edit only those.

Generally you shouldn't delete keys unless there is some specific requirement in your app to do so. What you should do is to set default values for each of your keys when the app starts:

[[NSUserDefaults standardUserDefaults] registerDefaults:@{... : ...}];

These defaults will be valid while the app is running but won't be saved. If you set anything using any of the set...:forKey: methods and synchronize then they will overwrite the defaults and be saved.

Answer 2

Try this

- (NSDictionary *) dictionaryRepresentation . Using this method on the standard user defaults, you can get a list of all keys in the user defaults. You can then use this to clear the user defaults:

    NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];
    NSDictionary * dict = [defs dictionaryRepresentation];
    for (id key in dict) {
        [defs removeObjectForKey:key];
    }
    [defs synchronize];

removeObjectForKey -- that should give you the ability to remove a preference.

Answer 3

You can remove everything in NSUserDefaults associated with your app by calling this.

// remove entire user defaults
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
[[NSUserDefaults standardUserDefaults] synchronize]; // not sure if needed, but never hurts

This should give you a clean slate for saving information to user defaults.