Backbone and Rails associations: Avoiding JSON HashWithIndifferentAccess errors

Question

I\'m trying to get my backbone associations working inside a rails app , and I\'m having difficulty when trying to update existing models. Specifically, Rails throws the followi

Answer 1

I dealt with the same issue recently. It's actually not a HashWithIndifferentAccess error: it has to do with how accepts_nested_attributes_for expects params.

When you declare accepts_nested_attributes_for :comments, Rails looks for a parameter call comments_attributes on the incoming params.

The problem is that your JSON representation coming from Backbone has a "comments" property instead of a "comments_attributes" property.

You could fix it on the Backbone side by adding a toJSON function to your Post model:

# in your Post model
toJSON: ->
  attrs = _.clone(@attributes)
  attrs.comments_attributes = _.clone(@attributes.comments)
  delete attrs.comments
  attrs

Or you could handle it in your Rails controller:

# in your Posts controller
def update
  params[:comments_attributes] = params.delete(:comments) if params.has_key? :comments
  # call to update_attributes and whatever else you need to do
 end

Hopefully this helps.

Answer 2

For those who are Googling...

While the current accepted answer certainly works, the following was how I worked out my problem (very similar, but slightly different):

I was using a nested form, with models nested 4 layers deep. In my controller which was rendering the form, I needed to build out the form.

def new
  @survey = Survey.new
  3.times do
    question = @survey.questions.build
    4.times { question.answers.build }
  end
end

This allowed the params to include params[:survey][:questions_attributes]. Rails renamed the parameters for me because I informed it ahead of time.

Hope this helps!