Creating a custom type for Mongo's ID's

[EwanValentine]

Apologies, I raised a similar ticket a while back but I just thought I'd raise a more specific question than my previous closed ticket. #393

For some context, when you generate protobuf code, say...

message Hello {
  string id = 1;
}

You would get

type Hello struct {
  Id string
}

Which means I have to do a bunch of conversion in order to use these structs as Mongodb models. As Mongodb's mgo driver requires a bson.ObjectId custom type for the ID field. Also the ID field is all uppercase as per Golang's own linting/style guide. Whereas protobuf generates them as Id.

So given that, is there a way I can create a custom type which would generate mgo compatible ID fields? Such as...

message Hello {
  BsonID id = 1;
}

generates...

type Hello struct {
    ID bson.ObjectId
}

I just wondered how to go about creating a custom type for this use-case?

I noticed someone had a PR of a similar nature a while back which wasn't approved/merged: #320

Thanks in advance!

[pbdeuchler]

We use bytes in our proto definitions and it works very well

[EwanValentine]

@pbdeuchler Do you need to manually convert between the two at runtime still? Did you need to limit the bytes to 12 in your protobuf def?

[EwanValentine]

Oh yeah it is just bytes under the hood! https://godoc.org/github.com/pkg/bson#ObjectId

[dsnet]

Closing this in favor of #52.

[bazaglia]

@EwanValentine @pbdeuchler have you tried the official mongodb go driver? I couldn't get it working: could not greet: rpc error: code = Unknown desc = cannot decode objectID into a *[]byte exit status 1

[amsokol]

Hi, look at this one:
https://github.com/amsokol/mongo-go-driver-protobuf
It supports ObjectId also.

[mihai1voicescu]

ObjectId can be replaced with a simple string in proto now

[Tobi696]

@mihai1voicescu Could you show the example code? Either it doesn't work for me or I didn't get you right.

[mihai1voicescu]

Unfortunately I put that project on hold before I could finish but this is what I used:

message Person {
    string  id = 1 [(tagger.tags) = "bson:\"_id,omitempty\""];

Which generates:

type Person struct {
	Id                   string           `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty" bson:"_id,omitempty"`

As far as I remember (so I might be wrong) you are then free to insert the structs in Mongo and it will generate an ID if the struct.id == "" which you can get with:

query, err := itemCol.InsertOne(ctx, &req.Item)
...
oid, ok := query.InsertedID.(primitive.ObjectID)
	if !ok {
		panic("Unable to convert")
	}

	res := mn.CreateResponse{Id: oid.Hex()}

Note that I had one more problem with the ID, but I can't remember what it was or if I solved it.

Hope it helps! If not maybe you can post the exact exception/st/problem.

Please note that I am not an expert in go so the above code might not be production ready.

[pravchuk]

Has this been solved or not yet?