newgist2.swift

struct YourUserDefaults {
    ...
    func set(_ value: Any?, for key: String) {
        // some encrypt work
        ...
        UserDefaults.standard.set(ValueAfterEncrypt, forKey: key)
    }
    
    func object(for key: String) -> Any?{
        let value = UserDefaults.standard.value(forKey: key)
        // some decrypt work
        ...
        return ValueAfterDecrypt
    }
}

struct Manager {
    static var datas: [SomeModel] = YourUserDefaults.standard.value(forKey: "datasKey") as? [SomeModel] ?? [] {
        didSet {
            DispatchQueue.global().async {
                // some archive work, maybe map to a json Array
                ...
                YourUserDefaults.standard.set(datas, forKey: "datasKey")
            }
        }
    }
}
// all in memory
Manager.datas[2] = Manager.datas[0] + Manager.datas[1]