9.swift

enum PersonCodingKeys: String, CodingKey {
  case name
  case pets
}

// CHALLENGE 1: Nested Heterogeneous Array Decoded.
required init(from decoder: Decoder) throws {
  let container = try decoder.container(keyedBy: PersonCodingKeys.self)
  name = try container.decode(String.self, forKey: .name)
  
  // Get the container containing the whole list of pets.
  var petsContainer = try self.nestedUnkeyedContainer(forKey: key)
  // Initialise empty list of pets.
  var pets = [Pet]()
  var tmpContainer = petsContainer
  // For each pet...
  while !container.isAtEnd {
    // Get the container containing the type of the pet.
    let typeContainer = try petsContainer.nestedContainer(keyedBy: Discriminator.self)
    // Decode the PetFamily type from the type container.
    let family: PetFamily = try typeContainer.decode(PetFamily.self, forKey: PetFamily.discriminator)
    // Decode the correctly mapped type according to the family.
    if let type = family.getType() as? Pet.Type {
      pets.append(try tmpContainer.decode(type))
    }
  }
  self.pets = pets
}