EnumWithAssociatedValueEncodable.swift

import Foundation


struct SomeObject: Codable {
    let name: String
}

struct OtherObject: Codable {
    let number: Int
}

let data = """
[{
  "type": "first",
  "name": "Test"
}, {
  "type": "second",
  "number": 10
}]
""".data(using: .utf8)!

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

    enum CodingKeys: CodingKey {
        case type
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let type = try container.decode(String.self, forKey: .type)

        switch type {
        case "first":
            try self = .first(SomeObject(from: decoder))
        case "second":
            try self = .second(OtherObject(from: decoder))
        default:
            let context = DecodingError.Context(codingPath: decoder.codingPath,
                                                debugDescription: "Unexpected type: \(type)")
            throw DecodingError.dataCorrupted(context)
        }
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        switch self {
        case .first(let obj):
            try container.encode("first", forKey: .type)
            try obj.encode(to: encoder)
        case .second(let obj):
            try container.encode("second", forKey: .type)
            try obj.encode(to: encoder)
        }
    }
}

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

 [__lldb_expr_66.TargetEnum.first(__lldb_expr_66.SomeObject(name: "Test")),
 __lldb_expr_66.TargetEnum.second(__lldb_expr_66.OtherObject(number: 10))]
 */

print("\n\n---------------- encode -------------------")
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
let encoded = try! encoder.encode(decoded)
print(String(decoding: encoded, as: UTF8.self))

// https://www.hackingwithswift.com/example-code/language/how-to-format-json-using-codable-and-pretty-printing
print("\nDone")