Question

My setup: Rails 2.3.10, Ruby 1.8.7

I have experimented, without success, with trying to access a virtual attribute in a model from a JSON call. Let’s say I have the following models and controller code

class Product
 name,
 description,
 price,
 attr_accessor :discounted_price 
end

class Price
 discount
end

class ProductsController
 def show
  @product = Product.find(params[:id])
  respond_to do |format|
   format.html # show.html.erb
   format.json { render :json => @product }                                     
  end
 end
end

What I like is to have the JSON output also include Product.discounted_price which is calculated in real-time for each call, ie discounted_price = Price.discount * Product.price. Is there a way to accomplish this?

SOLUTION:
With the initial help from dmarkow, I figured it out, my actual scenario is more complex than the above example. I can do something like this, in the Product model, add a getter method

def discounted_price
 ...# do the calculation here
end

In the JSON call do this

store = Store.find(1)
store.as_json(:include => :products, :methods => :discounted_price)

Answer 1

You can run to_json with a :methods parameter to include the result of those method(s).

render :json => @product.to_json(:methods => :discounted_price)