Question

On page load I’m bootstrapping my data to my collections via this technique. That works great, but I’m running into an issue where I have sub-models which also need to be cast.

For example, I return a JSON collection called Book, and each book array contains 10-20 models themselves called Pages. If I try and access Pages directly, I get the [object][object] error as Backbone can’t figure out what type of object it is.

Previously when I was using fetch, I would get around this by using collections which contained a parse action. In parse I would do something like:

Collection_Books = Backbone.Collection.extend({
    model: Model_Book,
    parse: function (response) {
        response.Pages = new Collection_Pages(response.Pages);
        return response;
    }
});

Now that I’m accessing the data directly and not using fetch, the documentation implies that I no longer have access to the parse method.

If I am not using fetch or calling a server on page load, how can I cast sub-models using the Books > Pages example?

Answer 1

Update: This answer is now out of date, see uglymunky’s answer for more up to date information.

---

You’re right, parse is only specified to be called during fetch so it won’t be called when you’re building a collection from raw data.

But, since you control the raw data that you’re using to bootstrap your collection, you can call your collection’s parse yourself:

var c = new YourCollection(
    YourCollection.prototype.parse([
        // attribute data goes here...
    ])
);

Demo: http://jsfiddle.net/ambiguous/kdaZ3/

Your parse methods (both collection and model) shouldn’t care about their calling context so calling them directly from the prototype should be fine.