如何通过Go要求protoc使用值而不是指针作为映射的值侧？

Question

I am using protocol buffers defined like this:

message Index {
     message albums {
         repeated string name = 1;
     }
     map<string, albums> artists_albums= 1;
     map<int32, albums> year_albums = 2;
}

It generates go code like this:

type Index struct {
    ArtistsAlbums map[string]*IndexAlbums
    YearAlbums     map[int32]*IndexAlbums
 }

How can I make it generate map values of type IndexAlbums instead of *IndexAlbums?

Answer 1

If you use gogoprotobuf then there is an extension that will allow that

map<string, albums> artists_albums = 1 [(gogoproto.nullable) = false];

With regular goprotobuf I don't believe there is a way.

nullable, if false, a field is generated without a pointer (see warning below).

Warning about nullable: According to the Protocol Buffer specification, you should be able to tell whether a field is set or unset. With the option nullable=false this feature is lost, since your non-nullable fields will always be set. It can be seen as a layer on top of Protocol Buffers, where before and after marshalling all non-nullable fields are set and they cannot be unset.