UserDefaults PropertyWrapper

gistfile1.txt

import Foundation

@propertyWrapper struct UserDefaultsWrapper<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 {
            if let value = newValue as? OptionalProtocol, value.isNil() {
                UserDefaults.standard.removeObject(forKey: key)
            } else {
                UserDefaults.standard.set(newValue, forKey: key)
            }
        }
    }
}
 
fileprivate protocol OptionalProtocol {
    func isNil() -> Bool
}

extension Optional: OptionalProtocol {
    func isNil() -> Bool {
        return self == nil
    }
}