Question

I’m trying to set up an item model and a tag model that have a many-to-many relationship (items have multiple tags and tags belong to multiple items). I’m using Rails and Backbone.js, so I need to have them store, retrieve and update models seamlessly between each other. I would also love it if I could save a new list of tags for a specific item in one go from the client.

What’s the correct way to structure the models and controllers on the Rails side and the models on the Backbone side to keep the system RESTful and make it easy to share models between them? Specifically, what would the API look like on the server, and what would the JSON representation of the models be in saving and retrieving them?

I would really appreciate any advice on structure, and I don’t really need any code or implementation details — just a high level setup would be great. Thanks!

Answer 1

[In addition to Pope’s answer:]

For reference, the Rails answer (from Creating multiple resources in a single RESTful POST in rails) is to use accepts_nested_attributes_for:

class Item < ActiveRecord::Base
  has_many_and_belongs_to :tags
  accepts_nested_attributes_for :tags
end

class Tag < ActiveRecord::Base
  has_many_and_belongs_to :items
end

The following assumes that you’ve added ActiveRecord::Base.include_root_in_json = false to one of your initializers (see here for why).

To save a list of tags for an item from Backbone, the answer (from Saving nested objects with Rails, backbone.js, and accepts_nested_attributes_for) is to override sync on the Item model:

sync: (method, model, options) ->
    data = JSON.stringify model.toJSON()
    if (method == "create" || method == "update")
        json = model.attributes
        json = _.extend json, {tags_attributes: model.tags.toJSON()}
        data = JSON.stringify json

    options.data = data
    options.contentType = 'application/json'
    Backbone.sync method, model, options

This solution might require a bit more hackery to get Rails to understand Backbone, but this is how you would start setting them up.