UserDefaultExtensions

// https://www.vadimbulavin.com/advanced-guide-to-userdefaults-in-swift/
// what is the difference between WWDC2019 https://devstreaming-cdn.apple.com/videos/wwdc/2019/402fd460n3p3w5c/402/402_whats_new_in_swift.pdf
// The marker protocol
protocol PropertyListValue {}

extension Data: PropertyListValue {}
extension String: PropertyListValue {}
extension Date: PropertyListValue {}
extension Bool: PropertyListValue {}
extension Int: PropertyListValue {}
extension Double: PropertyListValue {}
extension Float: PropertyListValue {}

// Every element must be a property-list type
extension Array: PropertyListValue where Element: PropertyListValue {}
extension Dictionary: PropertyListValue where Key == String, Value: PropertyListValue {}


struct Key: RawRepresentable {
    let rawValue: String
}

extension Key: ExpressibleByStringLiteral {
    init(stringLiteral: String) {
        rawValue = stringLiteral
    }
}

@propertyWrapper
struct UserDefault<T: PropertyListValue> {
    let key: Key

    var wrappedValue: T? {
        get { UserDefaults.standard.value(forKey: key.rawValue) as? T }
        set { UserDefaults.standard.set(newValue, forKey: key.rawValue) }
    }
}


extension Key {
    static let isFirstLaunch: Key = "isFirstLaunch"
}
struct Storage {
    @UserDefault(key: .isFirstLaunch)
    var isFirstLaunch: Bool
}