can a backbone.js model contain multiple collections?

Question

I'm just starting out with backbone.js and trying to wrap my head around the modeling concepts. I want to use backbone js to create a shopping cart app, interfacing with a 3rd party REST api (not rails, can't modify).

This is the JSON response example for GET cart contents:

        {
          "_v" : "12.3",
          "currency" : "USD",
          "product_sub_total" : 96.00,
          "product_total" : 86.00,
          "shipping_total" : null,
          "tax_total" : null,
          "order_total" : null,
          "product_items" : 
          [
            {
              "product_id" : "123",
              "item_text" : "Product foo",
              "quantity" : 2.00,
              "product_name" : "foo",
              "base_price" : 30.00,
              "price" : 60.00
            },
            {
              "product_id" : "456",
              "item_text" : "Product foo",
              "quantity" : 1.00,
              "product_name" : "bar",
              "base_price" : 40.00,
              "price" : 40.00,
              "price_adjustments" : 
              [
                {
                  "promotion_id" : "10% off",
                  "promotion_link" : "http://example.com/dw/shop/v12_3/promotions/10_percent_off",
                  "item_text" : "10% off",
                  "price" : -4.00
                }
              ]
            }
          ],
          "order_price_adjustments" : 
          [
            {
              "promotion_id" : "10$ off",
              "promotion_link" : "http://example.com/dw/shop/v12_3/promotions/10_bugs_off",
              "item_text" : "10$ off",
              "price" : -10.00
            }
          ]
        }

Looking at this JSON data, there are aggregate pieces of data like "product_total", and "shipping_total", and there are lists contained within like "product_items" and "order_price_adjustments". Even individual "product_items" can also have nested list of "price_adjustments".

How can I model this shopping cart in backbone.js? Should I create a model for every hash that I see ("product_item", "price_adjustment") and then model a collection of those models and then make a basket model that contains those collections as well as aggregate datas? I'm not sure how to approach this...

I'm new to Backbonejs but I'm pretty sure that Collections are a group of multiple models. Not the other way around. — Jake Wilson, Jan 13 '15 at 01:27

score 4 · Answer 1 · answered Jul 26 '12 at 19:08

You can really do this however you want. If you don't need to do anything with the items or price adjustments data beyond access it, I'd just leave it as a JavaScript object. If you want to define functions to transform and work with that data, I'd define Item and PriceAdjustment models.

Of course, your ShoppingCart model can have attributes called items and priceAdjustments which are Backbone collections containing these models. If you end up not defining them as models, just leave them as normal arrays.

I tend to err on the side of creating Backbone models, as it's trivial to do and will save you the trouble of further down the road deciding you should have defined them as Backbone models in the first place.

In brief, I'd probably end up with a ShoppingCart model with Backbone Items and PriceAdjustments collections containing Item and PriceAdjustment models. i.e. shoppingCart.get('items') would return your collection of Items.

can a backbone.js model contain multiple collections?

1 Answers1