readonly, copy) NSString *name; @property (nullable, nonatomic, copy) NSString *email; - (nonnull instancetype)initWithName:(nonnull NSString *)name; - (nonnull instancetype)init; @end let user = User(name: "hogehoge") user.email = "test@test.com" print("\(user.name) \(user.email ?? "no email")") // hogehoge test@test.com