Populating data from referenced models in different modules in MEAN.JS - angularjs

Question

I am absolutely new to the MEAN stack, and I am using the MEAN.js(ver 0.4.2) generator for my project.
I am using the default users module and created a new module 'Topics' using the module generator. I have a basic role based login system using the users module where users can sign up and see/edit their profiles. In the profile, there is a reference to the topics module's mongoose model called 'Topics'.
topic.server.model.js looks like this(this is the schema for the topics) :
//Topic Schema
var TopicSchema = new Schema({
.......
user: {
type: Schema.ObjectId,
ref: 'User'
}
});
mongoose.model('Topic', TopicSchema);
The content from this model can access the data from the users model. But the i cant get the items to show from the topics model, when i am referencing them from the users module.
My users model has this in the schema :
var UserSchema = new Schema({
......
interest: [{
type: Schema.Types.ObjectId,
ref: 'Topic'
}],
skills: [{
type: Schema.Types.ObjectId,
ref: 'Topic'
}]
});
mongoose.model('User', UserSchema);
I am trying to populate the data from topics using the following middleware :
exports.userByID = function (req, res, next, id) {
if (!mongoose.Types.ObjectId.isValid(id)) {
return res.status(400).send({
message: 'User is invalid'
});
}
User.findById(id, '-salt -password').populate('interest', 'name').populate('skills', 'name').exec(function (err, user) {
if (err) {
return next(err);
} else if (!user) {
return next(new Error('Failed to load user ' + id));
}
req.model = user;
next();
});
};
I would need a little guidance as to how do i get the data in front end to show, something like {{user.interest.name}}.
Edit
In the users.profile.server.controller, the json is not getting created from this :
exports.me = function (req, res, next) {
var id = req.user._id;
User.findOne({
_id: id
}).populate('interest', 'name').populate('skills', 'name').exec(function(err, userData) {
if (err) return next(err);
if (!userData) return next(new Error('Failed to load User ' + id));
res.json(userData || null);
next();
});
};
Getting the following error in the terminal :
GET /api/users/me 400 22.173 ms - -
Error: Can't set headers after they are sent.