How can I include a model association in a JSON response in Rails?

I've looked at similar posts but can't seem to quite figure it out.

I have the following function which works just fine. The Listing model has a foreign key called price_id which maps to the Price model and its price_range column. Price_id is returned as part of the message object in the JSON response开发者_StackOverflow社区.

How can I return the corresponding price_range value from the association instead of the price_id value (as part of the message obj, and keep the other attributes)?

def update
    @listing = Listing.find(params[:listing][:id])

    #if params were passed in for updating
    if @listing.update_attributes(params[:listing])
    #should we return the whole thing or just what's needed?
        json_response = {
             "success" => @listing.save, #save to DB and assign true/false based on success...
             "message" => @listing.attributes #USE attributes to show output the content of the @message obj, and not another object called "message"
        }

        respond_to do |format| 
            #json response
            format.html { render:json => json_response } 
            format.xml { render :xml => @listing } 

            #normal response. Consider leaving this for now?
            #format.html { render :action => "detail" } #refresh this page, with new data in it. Consider trying to use redirect instead?
            #format.xml  { head :ok }
        end
    end #end if 

end

add a method in your Listing model with the price_range and call it in serializable_hash

class Listing

  def price_range
    price.price_range
  end
end

Like explain on comment you can use delegate instead this method :

class Listing
  delegate :prince_range, :to => price
end

In you controller you can now do :

   json_response = {
         "success" => @listing.save, #save to DB and assign true/false based on success...
         "message" => @listing.serializable_hash(:methods => [:price_range])
    }

Based on what I read in this article, you should be able to do this:

class Listing
  def as_json
    super(:include => :price)
  end
end

Then in your controller:

json_response = {
  "success" => @listing.save,
  "message" => @listing.as_json
}

If I understand correctly, you want to add @listing.price.price_range value to the "message" ? If so, try this:

"message" => @listing.attributes[:price_range] = @listing.price.price_range