Managing UserDefault with property wrappers

howToUse.swift

// 使用例
struct Settings {
    @UserDefault(key: "userName", defaultValue: "Unknown")
    static var userName: String
}

// 値の保存
Settings.userName = "Alice"

// 値の取得
print(Settings.userName) // Alice

ManageUserDefault.swift

import Foundation

@propertyWrapper
struct UserDefault<T> {
    let key: String
    let defaultValue: T

    init(key: String, defaultValue: T) {
        self.key = key
        self.defaultValue = defaultValue
    }

    var wrappedValue: T {
        get {
            return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
        }
        set {
            UserDefaults.standard.set(newValue, forKey: key)
        }
    }
}