user-defaults-storage

User Defaults Settings Storage and Reading

✅ RECOMMENDED - KVO Pattern with KeyValueStore

Use the KVO pattern with KeyValueStore for all new persistent settings:

// ✅ CORRECT - KVO pattern with KeyValueStore
struct AppearancePreferencesUserDefaultsPersistor: AppearancePreferencesPersistor {

    enum Key: String {
        case newTabPageIsOmnibarVisible = "new-tab-page.omnibar.is-visible"
        case newTabPageIsProtectionsReportVisible = "new-tab-page.protections-report.is-visible"
        case userPreferences = "user.preferences"
        case lastUpdateCheck = "last.update.check"
    }

    private let keyValueStore: KeyValueStoring

    init(keyValueStore: KeyValueStoring) {
        self.keyValueStore = keyValueStore
    }

    var isOmnibarVisible: Bool {
        get { (try? keyValueStore.object(forKey: Key.newTabPageIsOmnibarVisible.rawValue) as? Bool) ?? true }
        set { try? keyValueStore.set(newValue, forKey: Key.newTabPageIsOmnibarVisible.rawValue) }
    }

    var isProtectionsReportVisible: Bool {
        get { (try? keyValueStore.object(forKey: Key.newTabPageIsProtectionsReportVisible.rawValue) as? Bool) ?? false }
        set { try? keyValueStore.set(newValue, forKey: Key.newTabPageIsProtectionsReportVisible.rawValue) }
    }

    var userPreferences: [String: String] {
        get { (try? keyValueStore.object(forKey: Key.userPreferences.rawValue) as? [String: String]) ?? [:] }
        set { try? keyValueStore.set(newValue, forKey: Key.userPreferences.rawValue) }
    }

    var lastUpdateCheck: Date {
        get { (try? keyValueStore.object(forKey: Key.lastUpdateCheck.rawValue) as? Date) ?? Date.distantPast }
        set { try? keyValueStore.set(newValue, forKey: Key.lastUpdateCheck.rawValue) }
    }
}

Key Guidelines for KVO Pattern

1. Use struct conforming to protocol - Follow the persistor pattern
2. Define keys as enum with String raw values - Use kebab-case for key names
3. Use KeyValueStoring protocol - Not direct UserDefaults access
4. Computed properties with get/set - Handle storage operations in accessors
5. Use try? for error handling - KeyValueStore operations can throw
6. Provide default values - Use nil coalescing operator (??) for defaults
7. Inject KeyValueStore in init - Enable dependency injection and testing