Backbone.Collection get model by id

Question

I have a collection that fetches models from server.

This works, now I want to grab a model by its id with MyCollection.at(0) and I get:

Answer 1

Have you set Model.idAttribute on the Model?

var Model = Backbone.Model.extend({
    idAttribute:"_id"
});

By default Backbone expects the id property be called id. When the idAttribute has been set, Backbone standardizes handling of ids so that model.id is always available, even if the id property is called something else. The original id property is available in the Model's attributes hash, and as such via the get methd. So:

model.id === model.get('_id') // -> true

Answer 2

You can use the cid (client-side ID) attribute of the model as an argument to MyCollection.get(), which is guaranteed to exist from creation on. The documentation seems to think that will work, see http://backbonejs.org/#Collection-get.