Initialising structs

When you have a private constant in your struct, you will need to specify a constructor (ie. an init) in order to initialise it using the parameters.

i.e.

struct Cake {
        var cost: Double { return rawAmount.asDouble }

        private let rawCost: Decimal

        enum CodingKeys: String, CodingKey {
            case rawCost = "amount" // server is sending a Decimal but we want to use a Double
        }
}

So if you want to use the above struct, ideally you would write:

let cake: Cake = .init(cost: 7.22)

However you can't do that, it will only want to initialise from Data or Decoder.

You need to explicitly write an initialiser inside the struct:

init(cost: Double) {
     rawCost = Decimal(cost)
}