Code to parse JSON in an enum

SpaceshipPlanet.swift

struct Spaceship: Codable {
    var name: String
    var model: String
}

enum SpaceshipPlanet {
    case spaceship(Spaceship)
    case planet(String)
}

extension SpaceshipPlanet: Decodable {
    enum CodingKeys: String, CodingKey {
        case spaceship
        case planet
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        if let ship = try container.decodeIfPresent(Spaceship.self, forKey: .spaceship) {
            self = .spaceship(ship)
        } else {
            self = .planet(try container.decode(String.self, forKey: .planet))
        }
    }
}

//...
let jsonDecoder = JSONDecoder()

do {
    let data = try jsonDecoder.decode([SpaceshipPlanet].self, from: jsonData!)
    data.forEach({ print($0) })
} catch {
    print("parse error")
}