Dictionary extension for using @AppStorage

I understand I need to make Dictionary conform to RawRepresentable when using a dictionary with @AppStorage. Below is the furthest I got.

extension Dictionary: RawRepresentable where Key == String, Value == String {
    public init?(rawValue: String) {
        guard let data = rawValue.data(using: .utf8),  // convert from String to Data
            let result = try? JSONDecoder().decode([String:String].self, from: data)
        else {
            return nil
        }
        self = result
    }

    public var rawValue: String {
        guard let data = try? JSONEncoder().encode(self),   // data is  Data type
              let result = String(data: data, encoding: .utf8) // coerce NSData to String
        else {
            return "[:]"  // empty Dictionary respresented as String
        }
        return result
    }

}

The extension compiles. But when I declare an empty dictionary it didn’t work:

@AppStorage private var data :  [String:String] = [:]

The error message is Missing argument for parameter #2 in call

What’s wrong with the codes?

>Solution :

You are missing the string key for the storage:

@AppStorage("data") private var data :  [String:String] = [:]