如何从目标c中的settings.bundle中检索值？

Question

我创建了一个从settings.bundle设置和检索值的项目.我还在settings.bundle文件中设置了一些默认值.现在的问题是我将值检索为

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
loginName.text = [defaults objectForKey:@"login_name"];

它第一次显示为null,但是在iPhone应用程序设置中设置了值.如果我更改值或手动设置它,则可以正确检索值.

帮帮我

Answer 1

虽然您定义了默认设置,但它们并不真正存储为值.它们默认存储.如果您尝试读取它,则该值为null.默认设置是值为的另一个属性.但这并不意味着将默认值写为默认值.

我所做的是,首先,检查一些设置(我确定应该有一个值)是否存在任何设置.如果它没有任何东西,那么我写下所有的默认值.

这是一个例子.

在AppDelegate.m上我检查email_notificaciones_preference是否有值,如果没有,我将所有默认设置写入每个设置.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
    NSUserDefaults * standardUserDefaults = [NSUserDefaults standardUserDefaults];
    NSString * email_notificaciones_preference = [standardUserDefaults objectForKey:@"email_notificaciones_preference"];
    if (!email_notificaciones_preference) {
        [self registerDefaultsFromSettingsBundle];
    }

}

我用这个函数写默认值给每个元素.

#pragma NSUserDefaults
- (void)registerDefaultsFromSettingsBundle {
    // this function writes default settings as settings
    NSString *settingsBundle = [[NSBundle mainBundle] pathForResource:@"Settings" ofType:@"bundle"];
    if(!settingsBundle) {
        NSLog(@"Could not find Settings.bundle");
        return;
    }

    NSDictionary *settings = [NSDictionary dictionaryWithContentsOfFile:[settingsBundle stringByAppendingPathComponent:@"Root.plist"]];
    NSArray *preferences = [settings objectForKey:@"PreferenceSpecifiers"];

    NSMutableDictionary *defaultsToRegister = [[NSMutableDictionary alloc] initWithCapacity:[preferences count]];
    for(NSDictionary *prefSpecification in preferences) {
        NSString *key = [prefSpecification objectForKey:@"Key"];
        if(key) {
            [defaultsToRegister setObject:[prefSpecification objectForKey:@"DefaultValue"] forKey:key];
            NSLog(@"writing as default %@ to the key %@",[prefSpecification objectForKey:@"DefaultValue"],key);
        }
    }

    [[NSUserDefaults standardUserDefaults] registerDefaults:defaultsToRegister];

}

希望有所帮助.

Answer 2

如果有人需要它 - 我把答案从MIQUEL翻译成Swift(尽我所能,因为我还在学习):

var standardUserDefaults = NSUserDefaults.standardUserDefaults()
var us: AnyObject? = standardUserDefaults.objectForKey("your_preference")
if us==nil {
    self.registerDefaultsFromSettingsBundle();
}

而func registerDefaultsFromSettingsBundle:

func registerDefaultsFromSettingsBundle() {
    // this function writes default settings as settings
    var settingsBundle = NSBundle.mainBundle().pathForResource("Settings", ofType: "bundle")
    if settingsBundle == nil {
        NSLog("Could not find Settings.bundle");
        return
    }
    var settings = NSDictionary(contentsOfFile:settingsBundle!.stringByAppendingPathComponent("Root.plist"))!
    var preferences: [NSDictionary] = settings.objectForKey("PreferenceSpecifiers") as [NSDictionary];
    var defaultsToRegister = NSMutableDictionary(capacity:(preferences.count));

    for prefSpecification:NSDictionary in preferences {
        var key: NSCopying? = prefSpecification.objectForKey("Key") as NSCopying?
        if key != nil {
            defaultsToRegister.setObject(prefSpecification.objectForKey("DefaultValue")!, forKey: key!)
        }
    }
    NSUserDefaults.standardUserDefaults().registerDefaults(defaultsToRegister);  
}

Answer 3

更新为 Swift 3：

func registerDefaultsFromSettingsBundle() {

    let userDefaults = UserDefaults.standard

    if let settingsURL = Bundle.main.url(forResource: "Root", withExtension: "plist", subdirectory: "Settings.bundle"),
        let settings = NSDictionary(contentsOf: settingsURL),
        let preferences = settings["PreferenceSpecifiers"] as? [NSDictionary] {

        var defaultsToRegister = [String: AnyObject]()
        for prefSpecification in preferences {
            if let key = prefSpecification["Key"] as? String,
                let value = prefSpecification["DefaultValue"] {

                defaultsToRegister[key] = value as AnyObject
                debugPrint("registerDefaultsFromSettingsBundle: (\(key), \(value)) \(type(of: value))")
            }
        }

        userDefaults.register(defaults: defaultsToRegister)

    } else {
        debugPrint("registerDefaultsFromSettingsBundle: Could not find Settings.bundle")
    }
}