[protobuf] 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;
}




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#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;
  
  //const google::protobuf::FieldDescriptor *a11 = d->FindFieldByName("home");
  //cout << " home message : " << a11->name() << " "<< a11->type_name() << endl;
  //const google::protobuf::FieldDescriptor *a12 = a11->message_type()->FindFieldByName("id");
  //cout << " home field : " << a12->name() << " "<< a12->type_name() << endl;
  
  //r->SetInt32(sub_message,a11->message_type()->field(0),32);
  //cout << "Hello Proto! " << f.header() << endl;
  
  //const google::protobuf::FieldDescriptor *a1 = d->FindFieldByName("home");
  //const OneofDescriptor* oneof2_ = d->FindOneofByName("payload");
  //const google::protobuf::FieldDescriptor *a1 = oneof2_->field(0);
  //const google::protobuf::Reflection* rr = f.GetReflection();
  //Message *sub_message = rr->MutableMessage(f,a1);

  //cout << "Hello Proto! " << sub_message->DebugString() << endl;
  //r->MutableMessage(&f,a1->message_type()->FindFieldByName("id"));
  //r->SetInt32(&f, oneof2_->field(0)->containing_oneof(), 42);
  //cout << "Hello Proto! " << f.home().id() << endl;
  //cout << "Hello Proto! " << oneof2_->name() << " " << oneof2_->field_count() <<endl;

  return 0;
}

message.proto
Description: Binary data