Google protobuf repeated fields with C++ - c++

Question

I have a requirement to build the following Metadata message using serialized key value pairs in C++.
message MetadataValue {
string key = 1;
google.protobuf.Value value = 2;
}
message Metadata {
repeated MetadataValue metadata = 1;
}
So I can have the values for MetadataValue from the following for statement in C++.
Metadata metadata;
if (buffer.has_value()) {
auto pairs = buffer.value()->pairs();
for (auto &p : pairs) {
MetadataValue* metadataValue = metadata.add_metadata();
metadataValue->set_key(std::string(p.first));
// I don't know how to set the value for google.protobuf.Value
}
}
My question is whether my approach is correct ? Are there better alternatives and how to set the google.protobuf.Value in that above scenario ? A simple code snippet with the answer is much appreciated.

Answer 1

I think this code works, I just checked the generated APIs by protoc.
If the typeof(p.second) is not a google::protobuf::Value, you need to add conversion like
auto v = google::protobuf::Value();
v.set_number_value(p.second);
// or p.second is string
// v.set_string_value(p.second);
Metadata metadata;
if (buffer.has_value()) {
auto pairs = buffer.value()->pairs();
for (auto &p : pairs) {
MetadataValue* metadataValue = metadata.add_metadata();
metadataValue->set_key(std::string(p.first));
*metadataValue->mutable_value() = p.second;
// I don't know how to set the value for google.protobuf.Value
}
}
And I am using protoc version 3
syntax = "proto3";
import "google/protobuf/struct.proto";
message MetadataValue {
string key = 1;
google.protobuf.Value value = 2;
}
message Metadata {
repeated MetadataValue metadata = 1;
}