Get model with both id and query parameters - ember-data

Question

I have a route that should load a model (BatchDetail) and a number of related items (BatchItems). Since there are a great number of items I should be able to do pagination with the help of two request parameters, limit and offset.
Here is the route I set up:
App.BatchDetailRoute = Ember.Route.extend({
model: function(params) {
var store = this.get('store');
var adapter = store.get('adapter');
var id = params.batch_detail_id;
var rejectionHandler = function(reason) {
Ember.Logger.error(reason, reason.message);
throw reason
}
return adapter.ajax("/batch_details/" + id, "GET", {
data: { limit: 50, offset: 100 }
}).then(function(json) {
adapter.didFindRecord(store, App.BatchDetail, json, id);
}).then(null, rejectionHandler);
},
setupController: function(controller, model) {
return this.controllerFor('batchItems').set('model', model.get('items'));
}
})
This way, when I go to /batch_details/1 my REST adapter will fetch the correct data which I receive in json in the above code.
Now, the model hook should return a model object or a promise that can be resolved to a model object, and that's where the problem lies. In setupController (which runs after the model hook) model is set to undefined and so my code explodes.
That means that whatever adapter.ajax returns does not resolve correctly but instead returns undefined. I'm baffled, since the above mechanism is exactly how the different find methods in ember-data (findById, findByQuery, etc.) work and that's where I got my idea from.
Can you shed some light on what I'm not getting?
Thank you.