Rails validations app specific problems

Hi all,

I have a unique workflow where it's making the use of validations difficult.

My app is for internal use in my company and I have a funky implementation (inspired by the e-commerce Railscasts episodes) of a cart. I have products which when I "add to cart" creates an order with a state of "incomplete". The product is a line item of my order. Hope that makes sense.

Even though this is a little complicated, it works well (even though it may not be the best implementation - suggestions are welcome though!)

Now the problem is when I go to checkout and complete my order I want to validate certain things, like if my customer's order number is present (validates_presence_of). This should be easy, but since the order has ALREADY been created I need to validate the presence of an attribute.

Also, I can't just do this:

[code] validates_presence_of :customer_order_number, :on => :update [/code]

Because it generates a validation error on my '/cart' page which is where I can go and edit the product quantities for the client order.

**I'm sure the solution lies in validates_presence_of with the :if condition, but I just can't figure out how to make it work.**

Below is my related app code.

Orders Controller:

[code]   def update     @order = Orders.find(params[:id])

    respond_to do |format|         if @order.update_attributes(params[:order])           flash[:notice] = 'Your cart has been updated.'           format.html { redirect_to( current_cart_url ) }           format.xml { head :ok }         else           format.html { redirect_to( current_cart_url ) }           format.xml { render :xml => @order.errors, :status => :unprocessable_entity }         end     end

  end

  def cart     create_current_order unless current_order     @order = current_order   end

  def checkout     @order = current_order   end

  def complete_order     @order = current_order

    respond_to do |format|       if @order.update_attributes(params[:order])         @order.complete #sets order completed at date and state to 'complete'         flash[:notice] = 'Thank you! Your order is being processed.'         format.html { redirect_to( products_path ) }         format.xml { head :ok }       else         format.html { render :action => 'checkout' }         format.xml { render :xml => @order.errors, :status => :unprocessable_entity }       end     end

  end [/code]

I know this is kind of tough to understand, please let me know if you need more specifics or code. Thank you!

-Tony

The :if option is just the name of an instance method that returns whether the validation should run (eg if the status has some value or something like that)

Fred