Setting field of a Message inside Message Protobuf

c++, nested, protocol-buffers

Solution

Instead of

this->cbmsg->repomessage().set_nodeid(message[0]);

you'll need

this->cbmsg->mutable_repomessage()->set_nodeid(message[0]);

to set the `repomessage` field directly. `repomessage()` will return a `const CBMessage_RepoMessage&` that cannot be modified.

Problem

I have the following protobuf definition: ``` message CBMessage { required int32 type = 1; //defines the kind of message that we send optional RepoMessage repomessage = 2; message RepoMessage { optional int32 nodeid = 1; optional int32 timestampsec = 2; optional int32 timestampmicrosec = 3; } } ``` As you can note, the `repomessage` field is a field of the "outer" message `CBMessage`. I would like to access `nodeid` field (of the "inner" message `RepoMessage`) in order to modify this parameter. So I create a CBMessage object: ``` CBTxMessages::CBMessage* cbmsg; this->cbmsg = new CBTxMessages::CBMessage; ``` And I have tried to modify the `nodeid` field in this way: ``` this->cbmsg->repomessage().set_nodeid(message[0]); ``` Yet, I get the following error when I compile: error: pasar ‘const CBTxMessages::CBMessage_RepoMessage’ como el argumento ‘this’ de ‘void CBTxMessages::CBMessage_RepoMessage::set_nodeid(google::protobuf::int32)’ descarta a los calificadores [-fpermissive] (The error is in Spanish but I think that you can understand). A possible translation will be: "the 'this' argument of 'void CBTxMessages :: CBMessage_RepoMessage :: set_nodeid (google :: protobuf :: int32)' discards the qualifiers") I have investigated it and found that the problem is related to the fact that the "basic getter" of the `repomessage` field returns (`repomessage()`) is returned as const reference (thus it cannot be modified directly), but I do wish to modify it. How can I solve this ?

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