This piece of code shows how much propertyWrapper can be useful

UserDefault+PropertyWrapper.swift

@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)
        }
    }
}

struct MTUserDefaults {
    @UserDefault("isOnBoardingCompleted", defaultValue: nil)
    static var isOnBoardingCompleted: Bool?
}

// Usage
MTUserDefaults.isOnBoardingCompleted = true
print(MTUserDefaults.isOnBoardingCompleted)


// credit to https://www.avanderlee.com/swift/property-wrappers/