如何从 Objective-c/Swift 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。现在的问题是当我检索值时

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

第一次显示为 null，但值是在 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

虽然您定义了默认设置，但它们并没有真正存储为值。它们被存储为默认值。如果您尝试读取它，则该值为空。默认设置与值一样是另一个属性。但这并不意味着将默认值写入默认值。

我要做的是，首先，检查某个设置（我确定应该有一个值）是否存储了任何内容。如果它没有任何东西，那么我写所有的默认值。

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];
    }

}

这个函数是我用来给每个元素写默认值的。

#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];

}

希望对您有所帮助。

Answer 2

如果有人需要 - 我将答案从 MIQUEL 翻译成 Swift（尽我所能）：

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

还有函数 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

为 Swift 3 更新：

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

您可以像这样使用简单的属性包装器：

用法

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

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

---

这背后的代码实现：

设置捆绑包值存在于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) }
    }
}

根和孩子

您应该为根和子plists 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/从用户默认值中存储/恢复，包括已经符合可编码的所有 Swift 标准数据类型。

---

此外，您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访问任何键值，您可以查看this answer here

Answer 6

试试这个

注册设置包的默认值

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

在检索设置包值之前同步数据

[[NSUserDefaults standardUserDefaults] synchronize]