Convert JSON field to enum value about argo

[tonyd256]

it should be as simple as just making it conform to that protocol. Make CurrencyValue conform to JSONDecodable and then implement the decode method for it.

[Blackjacx]

I have now this:

extension CurrencyValue : JSONDecodable {
    static func create(rawValue: String) -> CurrencyValue {
        if let newValue = CurrencyValue(rawValue: rawValue) {
            return newValue
        }
        return .unknown
    }

    static func decode(j: JSONValue) -> CurrencyValue? {
        return CurrencyValue.create
            <^> j <|  "amount"
            <*> j <|  "currency"
    }
}

But I fail somehow at the implementation of the decode method. I didn't get the Idea of that functional operators yet. Can you give me a tip?

[tonyd256]

so your CurrencyValue type is an enum that represents a single string. To create an instance of the enum you have written the create function that takes a single string and parses it into a CurrencyValue instance. Now in the decode function you want to create that CurrencyValue with the string in the JSONValue using the create method.

without getting into what fmap and apply mean ... since your create function takes one parameter you should only give it one parameter ... in this example you are trying to pass in 2 parameters. Replace "amount" with "currency" and remove the second line.

[Blackjacx]

I tested this, but it didn't work. I now follow the idea to store whatever comes from the server as raw value and implement a parser function for every enum inside the model struct, to access the enum value... Maybe there is a more elegant solution to this.

The problem was probably that the JSONValue 'j' coming to decode() is already the value of the JSON field with the key currency, so there is nothing more to decode. I would just need to call the create function with the raw value. But then I think I circumvent the system and loose the error checking because I do not use the operators then... Am I at least a littl bit right :-D?

[tonyd256]

If j is already the value you want you could just do return CurrencyValue.create <^> j.value() or ... <^> String.decode(j)

[Blackjacx]

Ahhh cool thank you very much 👍
That saves a lot of work!

[tonyd256]

No problem. Closing this now.