如何从 Objective-c/Swift 中的 settings.bundle 中检索值？

Question

我创建了一个项目，用于设置和检索settings.bundle 中的值。我还在 settings.bundle 文件中设置了一些默认值。现在的问题是，当我

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

第一次检索值时，它显示为 null，但这些值是在 iPhone 应用程序设置中设置的。 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

尽管您定义了默认设置，但它们并未真正存储为值。它们被存储为默认值。如果您尝试读取它，则该值为空。默认设置是另一个属性，就像值一样。但这并不意味着将默认值写入为默认值。

我所做的是，首先，检查某些设置（我确信应该有一个值）是否存储了任何内容。如果它没有任何内容，那么我会编写所有默认值。

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];
    }

}

我用这个函数为每个元素写入默认值。

#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];

}

希望有帮助。

Answer 2

如果有人需要它 - 我将答案从 MIQUEL 翻译为 Swift（尽我所能，因为我仍在学习）：

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

以及 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")
    }
}

Answer 4

swift 2.1 的更新版本：

 func registerDefaultsFromSettingsBundle() {
    let userDefaults = NSUserDefaults.standardUserDefaults()

    if let settingsURL = NSBundle.mainBundle().URLForResource("Root", withExtension: "plist", subdirectory: "Settings.bundle"),
           settings = NSDictionary(contentsOfURL: settingsURL),
           preferences = settings["PreferenceSpecifiers"] as? [NSDictionary] {

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

                defaultsToRegister[key] = value
                NSLog("registerDefaultsFromSettingsBundle: (\(key), \(value)) \(value.dynamicType)")
            }
        }

        userDefaults.registerDefaults(defaultsToRegister);
    } else {
        NSLog("registerDefaultsFromSettingsBundle: Could not find Settings.bundle");
    }
}

Answer 5

您可以使用像这样的简单属性包装器：

用法

@SettingsBundleStorage(key: "storageUsage_preference")
var storageUsage: Double

_{注意，只需在变量前添加 @objc 即可 100% 兼容 Objective-C。}

---

其背后的代码实现：

设置捆绑包值位于 UserDefaults 中，因此您可以为其使用自定义 PropertyWrapper。以下包装器适用于任何 UserDefault 值，包括 SettingsBundle 的所有值。

属性包装器

@propertyWrapper
public struct SettingsBundleStorage<T> {    
    private let key: String

    public init(key: String) {
        self.key = key
        setBundleDefaults(plist: .root) // This is the main plist
        setBundleDefaults(plist: .child(name: "DeveloperOptions")) // This is an example child.
    }

    public var wrappedValue: T {
        get { UserDefaults.standard.value(forKey: key) as! T }
        set { UserDefaults.standard.set(newValue, forKey: key) }
    }
}

根和子级

您应该为根和子级 plist 传递以下枚举：

extension SettingsBundleStorage {

    enum PList {
        case root
        case child(name: String)

        var name: String {
            var file: String
            switch self {
            case .root: file = "Root"
            case .child(let name): file = name.replacingOccurrences(of: ".plist", with: "")
            }
            file.append(".plist")
            return file
        }
    }
}

如果需要，查找并设置默认值。

此包装器使用此函数查找捆绑包键的默认值：

extension SettingsBundleStorage {

    func setBundleDefaults(plist: PList = .root) {
        let settingsName                    = "Settings"
        let settingsExtension               = "bundle"
        let settingsPreferencesItems        = "PreferenceSpecifiers"
        let settingsPreferenceKey           = "Key"
        let settingsPreferenceDefaultValue  = "DefaultValue"

        guard let settingsBundleURL = Bundle.main.url(forResource: settingsName, withExtension: settingsExtension),
              let settingsData = try? Data(contentsOf: settingsBundleURL.appendingPathComponent(plist.name)),
              let settingsPlist = try? PropertyListSerialization.propertyList(
                from: settingsData,
                options: [],
                format: nil) as? [String: Any],
              let settingsPreferences = settingsPlist?[settingsPreferencesItems] as? [[String: Any]] else {
            return assertionFailure("Can not get the \(plist.name) from the bundle: \(settingsName)")
        }

        var defaultsToRegister = [String: Any]()

        settingsPreferences.forEach { preference in
            if let key = preference[settingsPreferenceKey] as? String {
                defaultsToRegister[key] = preference[settingsPreferenceDefaultValue]
            }
        }

        UserDefaults.standard.register(defaults: defaultsToRegister)
    }
}

此包装器可以将任何类型的可编码存储到用户默认值中或从用户默认值恢复，包括已经符合可编码的所有 Swift 标准数据类型。

---

此外，您还可以找到一个类似但代码更少的版本，用于从任何用户默认值访问任何键值，您可以查看这个答案在这里

Answer 6

试试这个

注册设置捆绑包的默认值

NSDictionary *appDefaults = [NSDictionary dictionaryWithObject:defaultValue forKey:@"key"];
 [[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];

在检索设置捆绑包值同步数据之前

[[NSUserDefaults standardUserDefaults] synchronize]