Property Wrapper in Swift

property-wrapper-3.swift

// We make our Property Wrapper Generic.
@propertyWrapper
struct Store<T> {

    // This is the key that user can provide
    var key: String
    
    // The default value for the property
    var defaultValue: T
    
    // Now it returns Generic value instead of Bool
    var wrappedValue: T {
        set { UserDefaults.standard.set(newValue, forKey: key) }
        get { UserDefaults.standard.value(forKey: key) as? T ?? defaultValue }
    }
    
    // We ask both key and default value during initialization. 
    init(key: String, defaultValue: T) {
        self.key = key
        self.defaultValue = defaultValue
    }
}

// Usage:
struct AppSettings {
    @Store(key: "app_user_name", defaultValue: "") static var userName: String
    @Store(key: "is_dark_mode_enabled", defaultValue: false) static var isDarkModeEnabled: Bool
}

AppSettings.userName = "Ironman"
AppSettings.isDarkModeEnabled = false