How to serialize/deserialize a protobuf message that uses 'oneof' with ScalaPB?

Question

I'm using ScalaPB to compile my Scala case classes for serializing my protobuf messages.

I have a .proto file with the following messages:

message WrapperMessage {
    oneof msg {
        Login login = 1;
        Register register = 2;
    }
}

message Login {
    required string email = 1;
    required string password = 2;
}

message Register {
    required string email = 1;
    required string password = 2;
    optional string firstName = 3;
    optional string lastName = 4;
}

How do I create my WrapperMessage knowing that I want to put a Login message inside the msg?

  val login = Login(email = "[email protected]", password = "testpass")
  val wrapperMessage = WrapperMessage(???)
  val wrapperMessageBytes = wrapperMessage.toByteArray

Let's say now that I am receiving a WrapperMessage over the wire; how do I deserialize the message using ScalaPB case class methods?

Answer 1

ScalaPB has documentation which clearly provides examples for the questions I am asking. In this answer I tailor the examples provided on ScalaPB towards my question.

To initialize a message with oneof:

val login = Login(email = "[email protected]", password = "testpass")
val wrapperMessage = WrapperMessage().withLogin(login)

To match against a message's oneof field:

wrapperMessage.msg match {
  case Msg.Login(l) =>  // handle l
  case Msg.Register(r) =>  // handle r
  case Msg.Empty =>  // handle exceptional case...
}

Answer 2

You should be able to initialize WrapperMessage with an empty constructor and call .set_login(login)

You would deserialize to WrapperMessage and pattern match on message.WhichOneof which returns either "login" or "register". Then you would call the accessor on that specific message (ie. message.login).