Modify data in Meteor.publish before sending down to client

Question

I have the following use case:

• I have a users table in MongoDB on the backend, which is a separate service than the frontend. I use DDP.connect() to connect to this backend service.
• Each user has a set of "subjects"

• Each subject in the users table is referenced by id, not name. There is a separate table called "subjects" that holds the subjects by id.

• I want to publish the user down to the client, however I want the published user to be populated with the subjects first.

I tried the following, inspired by this blog post:

// in the backend service on port 3030
Meteor.publish('users', function(userId) {
  var _this = this;
  Meteor.users.find({
    _id: userId
  }).forEach(function(user) {
    user.profile = populate(user.profile);
    console.log(user);
    _this.changed('users', userId, {
        _id: userId,
        profile: user.profile
    });
  });
  _this.ready();
});

// in the client
var UserService = DDP.connect('http://localhost:3030');

var UserServiceProfile = UserService.subscribe('users', Meteor.userId());
console.log(UserServiceProfile);

This gives the following error on the backend:
Exception from sub users id akuWx5TqsrArFnQBZ Error: Could not find element with id XhQu77F5ChjcMTSPr to change.

So I tried changing _this.changed to _this.added. I don't get any errors, but the changes aren't showing up in the client minimongo, even though I can see that the populate function worked through the console.log(user) line.

Answer 1

I'm not sure how you'd fix your code, but you might not need to. It looks like you want the https://atmospherejs.com/maximum/server-transform package.

Add the server-transform package to your project, and replace your code with this (I'm going to assume you also have underscore added to your project, and the subjects collection in your database corresponds to a global variable called Subjects in your code.):

Meteor.publishTransformed('users', function(userId) {
  return Meteor.users.find({
    _id: userId
  }).serverTransform({
    'profile.subjects': function(doc) {
      var subjects = [];
      _(doc.profile.subjects).each(function(subjectId) {
        subjects.push(Subjects.findOne(subjectId));
      });

      return subjects;
    }
  });
});