Swift 4 Codable; How to decode object with single root-level key

Question

I\'m using the Swift 4 Codable protocol with JSON data. My data is formatted such that there is a single key at the root level with an object value containing t

Answer 1

Of course, you can always implement your own custom decoding/encoding — but for this simple scenario your wrapper type is a much better solution IMO ;)

For comparison, the custom decoding would look like this:

struct User {
    var id: Int
    var username: String

    enum CodingKeys: String, CodingKey {
        case user
    }

    enum UserKeys: String, CodingKey {
        case id, username
    }
}

extension User: Decodable {
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)

        let user = try values.nestedContainer(keyedBy: UserKeys.self, forKey: .user)
        self.id = try user.decode(Int.self, forKey: .id)
        self.username = try user.decode(String.self, forKey: .username)
    }
}

and you still to conform to the Encodable protocol if you want to support encoding as well. As I said before, your simple UserWrapper is much easier ;)