Codable for enum with associated values

CodabeEnum.swift

import Foundation

enum TargetEnum: Codable {
  case first(SomeObject)
  case second(OtherObject)

  enum CodingKeys: CodingKey {
    case first
    case second
  }


    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let key = container.allKeys.first
        switch key {
        case .first:
            var nestedContainer = try container.nestedUnkeyedContainer(forKey: .first)
            let object = try nestedContainer.decode(SomeObject.self)
            self = .first(object)
        case .second:
            var nestedContainer = try container.nestedUnkeyedContainer(forKey: .second)
            let object = try nestedContainer.decode(OtherObject.self)
            self = .second(object)
        default:
            throw DecodingError.dataCorrupted(
                DecodingError.Context(
                    codingPath: container.codingPath,
                    debugDescription: "Unabled to decode enum."
                )
            )
        }
    }

    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)

        switch self {
        case .first(let object):
            var nestedContainer = container.nestedUnkeyedContainer(forKey: .first)
            try nestedContainer.encode(object)
        case .second(let object):
            var nestedContainer = container.nestedUnkeyedContainer(forKey: .second)
            try nestedContainer.encode(object)
        }
    }
}

struct SomeObject: Codable {
  let name: String
}

struct OtherObject: Codable {
  let number: Int
}

// Encoding
let anObject = SomeObject(name: "Hello, World!")
let valueToEncode = TargetEnum.first(anObject)

let encoded = try! JSONEncoder().encode(valueToEncode)
print(String(data: encoded, encoding: .utf8)!)

/* OUTPUT:
 {"type":"first","name":"Hello, World!"}
 */


// Decoding
let data = """
[{"first":
    [{"name":"Hello, World!"}]
},
{"second":
    [{"number":1}]
}]
""".data(using: .utf8)!

let decoded = try! JSONDecoder().decode([TargetEnum].self, from: data)
print(decoded)

/* OUTPUT:
 [__lldb_expr_23.TargetEnum.first(__lldb_expr_23.SomeObject(name: "Hello, World!")),
 __lldb_expr_23.TargetEnum.second(__lldb_expr_23.OtherObject(number: 1))]
 */