Kdan

class Pet: Codable {
  let name: String
}
class Cat: Pet {
  var lives: Int
}
class Dog: Pet {
  func fetch() { /**/ }
}

Kdan

{
  "name": "Kewin",
  "pets": [
    {
      "type": "Cat",
      "name": "Garfield",
      "lives": 9
    },
    {
      "type": "Dog",

Kdan

class Person: Codable {
  let name: String
  
  /// Retrieve the pets of the Person.
  func getPets(completion: ([Pet]) -> Void) throws {
    // Networking request omitted for simplicity.
    let data = responseData
    completion(try JSONDecoder().decode([Pet].self, from: data))
  }
}

Kdan

/// To support a new class family, create an enum that conforms to this protocol and contains the different types.
protocol ClassFamily: Decodable {
    /// The discriminator key.
    static var discriminator: Discriminator { get }

    /// Returns the class type of the object coresponding to the value.
    func getType() -> AnyObject.Type
}

/// Discriminator key enum used to retrieve discriminator fields in JSON payloads.

Kdan

/// The PetFamily enum describes the Pet family of objects.
enum PetFamily: String, ClassFamily {
    case cat = "Cat"
    case dog = "Dog"

    static var discriminator: Discriminator = .type

    func getType() -> AnyObject.Type {
        switch self {
        case .cat:

Kdan

class ClassWrapper<T: ClassFamily, U: Decodable>: Decodable {
    /// The family enum containing the class information.
    let family: T
    // The decoded object. Can be any subclass of U.
    let object: U?

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: Discriminator.self)
        // Decode the family with the discriminator.
        family = try container.decode(T.self, forKey: T.discriminator)

Kdan

class Person: Codable {
  let name: String
  
  /// Retrieve the pets of the Person.
  func getPets(completion: ([Pet]) -> Void) throws {
    // Networking request omitted for simplicity.
    let data = responseData
    completion(try JSONDecoder().decode([ClassWrapper<PetFamily, Pet>].self, from: data).compactMap { $0.object })
  }

Kdan

extension JSONDecoder {
    /// Decode a heterogeneous list of objects.
    /// - Parameters:
    ///     - family: The ClassFamily enum type to decode with.
    ///     - data: The data to decode.
    /// - Returns: The list of decoded objects.
    func decode<T: ClassFamily, U: Decodable>(family: T.Type, from data: Data) throws -> [U] {
        return try self.decode([ClassWrapper<T, U>].self, from: data).compactMap { $0.object }
    }
}

Kdan

/// Retrieve the pets of the Person.
func getPets(completion: ([Pet]) -> Void) throws {
  // Networking request omitted for simplicity.
  if let data = responseData {
      completion(try JSONDecoder().decode(family: PetFamily.self, from: data))
  }
}

Kdan

import Foundation

// MARK: - Model classes
/// The Pet superclass.
class Pet: Codable {
    /// The name of the pet.
    let name: String
    
    enum CodingKeys: String, CodingKey {
        case name