Can protobuf service method return primitive type?

protocol-buffers rpc protobuf-c
4ntoine picture 4ntoine · Mar 5, 2015 · Viewed 10.7k times · Source

I'm trying to use Google protobuf and i 'm having the next descriptions:

message.proto file:

message Request {
   required int32 id = 1;
   optional string value = 2;
}

service.proto file:

import "message.proto";

service Service {
    rpc request (Request) returns (bool);
}

I'm trying to generate c++ sources and getting an error:

$ protoc service.proto --cpp_out=/tmp/proto/build

service.proto:4:40: Expected message type.

Do i have to return user-defined types only? Are primitive (like bool or string) supported? Can i use primitive types as service method argument (instead of Request in my example)?

Answer

Kenton Varda picture Kenton Varda · Mar 7, 2015

No, you cannot use a primitive type as either the request or response. You must use a message type.

This is important because a message type can be extended later, in case you decide you want to add a new parameter or return some additional data.

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