Ruby on Rails - Render JSON for multiple models

Question

I am trying to render results from more than one model in JSON. The following code in my controller only renders the first result set:

  def calculate_quote
    @moulding = Moulding.find(params[:id])
    @material_costs = MaterialCost.all

    respond_to do |format|
      format.json  { render :json => @moulding }
      format.json  { render :json => @material_costs }
    end
  end

Any help would be much appreciated, thanks.

Answer 1

A controller can only return one response. If you want to send all these objects back, you have to put them in one JSON object.

How about:

def calculate_quote
  @moulding = Moulding.find(params[:id])
  @material_costs = MaterialCost.all
  response = { :moulding => @moulding, :material_costs => @material_costs }
  respond_to do |format|
    format.json  { render :json => response }
  end
end

Answer 2

I did something like

respond_to do |format|
      format.html # show.html.erb
      format.json { render :json => {:cancer_type => @cancer_type, :cancer_symptoms => @cancer_symptoms }}

here is the result

{"cancer_type":{"created_at":"2011-12-31T06:06:30Z","desc":"dfgeg","id":2,"location":"ffffd","name":"effffdd","sex":"ffffd","updated_at":"2011-12-31T06:06:30Z"},"cancer_symptoms":[]}

So it is working

Thank you guys

Answer 3

One way you could do this is to create a hash with the objects you want to render, and then pass that to the render method. Like so:

respond_to do |format|
  format.json  { render :json => {:moulding => @moulding, 
                                  :material_costs => @material_costs }}
end

If the models aren't associated through active record, that's probably your best solution.

If an association does exist, you can pass an :include argument to the render call, like so:

respond_to do |format|
  format.json  { render :json => @moulding.to_json(:include => [:material_costs])}
end

Note that you wouldn't have to retrieve the @material_costs variable in the section above if you take this approach, Rails will automatically load it from the @moulding variable.