codable_blogpost_custom_encoding.swift

enum Sex: String, Encodable {
  case male
  case female
  case other
}

struct User: Encodable {
  let id: Int
  let name: String
  let surname: String
  let sex: Sex
  
  private enum CodingKeys: String, CodingKey {
    case id
    case fullName = "full_name"
    case sex
  }
  
  func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(id, forKey: .id)
    try container.encode(name + surname, forKey: .fullName)
    try container.encode(sex, forKey: .sex)
  }
}

let user = User(id: 19, name: "John", surname: "Doe", sex: .male)
let encodedUserData = try! JSONEncoder().encode(user)

let json = try JSONSerialization.jsonObject(with: encodedUserData)