Set field onof type message using reflection in protobuf

[Gaurav Bhosale]

I am trying to set field of protobuf message.

My proto message look like,

package message;

message Packet

{

    required int32 header = 1;

    oneof payload

    {

        Home home = 2;

        Door door = 3;

    }

}

message Home {

    required int32 id = 1;

}

message Door {

    required int32 id = 1;

}

What I did,

Using SetInt32, I am able to set header field.

But when I am trying to set Home message fields ( oneof payload ), I am getting following errors.

I facing issue with setting field values of oneof message fields.

Output:

 header : header int32

 header value : 42

 Payload : payload 2

 home : home message

[libprotobuf FATAL google/protobuf/generated_message_reflection.cc:112] Protocol Buffer reflection usage error:

  Method      : google::protobuf::Reflection::SetInt32

  Message type: message.Packet

  Field       : message.Packet.home

  Problem     : Field is not the right type for this message:

    Expected  : CPPTYPE_INT32

    Field type: CPPTYPE_MESSAGE

terminate called after throwing an instance of 'google::protobuf::FatalException'

  what():  Protocol Buffer reflection usage error:

  Method      : google::protobuf::Reflection::SetInt32

  Message type: message.Packet

  Field       : message.Packet.home

  Problem     : Field is not the right type for this message:

    Expected  : CPPTYPE_INT32

    Field type: CPPTYPE_MESSAGE

Aborted (core dumped)

CPP code:

#include <iostream>

#include "proto/message.pb.h"

using namespace std;

using namespace google::protobuf;

int main(int argc, char const *argv[])

{

message::Packet f;

const google::protobuf::Descriptor *d = f.GetDescriptor();

const google::protobuf::FieldDescriptor *a = d->FindFieldByName("header");

cout << " header : " << a->name() << " "<< a->type_name() << endl;

const google::protobuf::Reflection* r = f.GetReflection();

r->SetInt32(&f, a, 42);

cout << " header value : " << f.header() << endl;

//const OneofDescriptor* oneof2_ = d->FindOneofByName("payload");

//cout << " Payload : " << oneof2_->name() << " " << oneof2_->field_count() <<endl;

const google::protobuf::FieldDescriptor *a11 = d->FindFieldByName("home");

const google::protobuf::FieldDescriptor *a1 = a11->message_type()->FindFieldByName("id");

cout << " home : " << a1->name() << " " << a1->type_name() <<endl;

const google::protobuf::Reflection* rr = f.GetReflection();

rr->SetInt32(&f, a1, 24);

cout << " home id value : " << f.home().id() << endl;

}

[Adam Cozzette]

I think the problem is that when you call rr->SetInt32(&f, a1, 24) you're trying to set a field inside a nested message inside f, which does not work. You can only set a field directly inside the message you're passing, so it should be something like rr->SetInt32(f->mutable_home(), a1, 24).

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