@t.ae ↓これじゃダメ？ @swiftbot
import Foundation struct DBUser: Codable { static let name: String = "user" var name: String init(name: String) { self.name = name } private enum CodingKeys : CodingKey { case name } init(from decoder: Decoder) throws { let container = try decoder.container(keyedBy: CodingKeys.self) let name = try container.decode(String.self, forKey: .name) self.init(name: name) } func encode(to encoder: Encoder) throws { var container = encoder.container(keyedBy: CodingKeys.self) try container.encode(name, forKey: .name) } } let u = DBUser(name: "hoge") let a = try! JSONEncoder().encode(u) print(String.init(data: a, encoding: .utf8)!)