Rails - Feb 2006 - adding to errors in controller?

def update
    @product = Product.find(params[:id])
    @product.attributes = params[:product]
    if params[:main_image]
      image = Image.new params[:main_image]
      if image.save
        @product.main_image.destroy if @product.main_image
        @product.main_image = image
      else
        @product.errors.add_to_base(image.errors.full_messages.join(",
"))
      end
    end

    if @product.errors.empty? and @product.save
      flash[:notice] = "Product was successfully updated"
      redirect_to :action => "show", :id => @product
    else
      render :action => ''edit''
    end
  end

Currently, products belong_to images, but later, I''ll probably have
products has_many images.

Say an image is invalid.  So it won''t be saved.  How do I properly
show that to the user?  The above is my approach, where I have to
manually add image.errors.full_messages to the product.errors.  But
then, I noticed that when an image had an error (and the error text
was added to product.errors), product still happily saved itself.  So
that''s why there''s a check in there for product.errors.empty?.

I know there''a  better way to do this that I''m missing...

Joe Van Dyk wrote:
>   def update
>     @product = Product.find(params[:id])
>     @product.attributes = params[:product]
>     if params[:main_image]
>       image = Image.new params[:main_image]
>       if image.save
>         @product.main_image.destroy if @product.main_image
>         @product.main_image = image
>       else
>         @product.errors.add_to_base(image.errors.full_messages.join(",
"))
>       end
>     end
> 
>     if @product.errors.empty? and @product.save
>       flash[:notice] = "Product was successfully updated"
>       redirect_to :action => "show", :id => @product
>     else
>       render :action => ''edit''
>     end
>   end
> 
> Currently, products belong_to images, but later, I''ll probably
have
> products has_many images.
> 
> Say an image is invalid.  So it won''t be saved.  How do I properly
> show that to the user?  The above is my approach, where I have to
> manually add image.errors.full_messages to the product.errors.  But
> then, I noticed that when an image had an error (and the error text
> was added to product.errors), product still happily saved itself.  So
> that''s why there''s a check in there for
product.errors.empty?.
> 
> I know there''a  better way to do this that I''m missing...
Calling save (or valid?) resets an object''s errors.  So your best
bet would be to add a "validates_associated :main_image" to the
Product
model. Then just save @product in your controller, which if valid
will automatically also save any new (un-saved) associated image.

This will also ensure that a valid new product image doesn''t get
saved if other parts of the product are invalid.

Prior to assigning the new image to the product, hold any old image
object in a variable so you can destroy it if the product save is
successful. You may be able to automate this in the model by
adding an attr_accessor called "new_main_image", and using this
instead of "main_image" in your view form.

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