struct Hoge: Codable { let id: Int private let jsonUrl: String? var url: URL? { return jsonUrl.flatMap(URL.init) } enum CodingKeys: String, CodingKey { case id case jsonUrl = "url" } } (edited)struct Hoge: Codable { let id: Int private let jsonUrl: String? var url: URL? { return jsonUrl.flatMap(URL.init) } enum CodingKeys: String, CodingKey { case id case jsonUrl = "url" } } (edited)