On Sun, May 8, 2011 at 12:00 PM, linda Keating <li...@ruby-forum.com> wrote:
> I'm learning with the Agile Web Development 4th edition book. I've
> built a method in my controller to test that it works, and now I want to
> move it to the model.
> ********************************
> *** line_item controller ***
> ********************************
> def create
> @cart = current_cart
> event = Event.find(params[:event_id])
> @line_item = @cart.add_event(event)
> new_capacity = event.capacity
>
>
> respond_to do |format|
> if @line_item.save
> new_capacity = new_capacity - @line_item.quantity
> event.capacity = new_capacity
> event.save
>
> format.html { redirect_to(@line_item.cart, :notice => 'Line item
> was successfully created.') }
> format.xml { render :xml => @line_item, :status => :created,
> :location => @line_item }
> else
> format.html { render :action => "new" }
> format.xml { render :xml => @line_item.errors, :status =>
> :unprocessable_entity }
> end
> end
> end
>
> so I started by doing this
>
> ***********************************
> *****line_item.rb****************
> ********************************
>
> def decrease_seat_capacity_on_create
>
> new_capacity = new_capacity - @line_item.quantity
> event.capacity = new_capacity
> event.save
> end
>
In this method @line_item does not exist because you have not created it. So
you may need to pass to this method the line_item object or look it up.
Also, you should look at the after_save callback in ActiveRecord, that way
you *might* be able to tell your LineItem model to automatically perform
this action after a successful save (if you google for activerecord
callbacks you will find a number of them, they are very useful).
>
> and made a changed the line_item controller like this
>
> respond_to do |format|
> if @line_item.save
> @line_item.decrease_seat_capacity_on_create
>
>
> But I get the error
>
> undefined method `quantity' for nil:NilClass
> Rails.root: c:/webtech/ServerSide/tickets_online
>
> Application Trace | Framework Trace | Full Trace
> app/models/line_item.rb:12:in `decrease_seat_capacity_on_create'
> app/controllers/line_items_controller.rb:51:in `block in create'
> app/controllers/line_items_controller.rb:49:in `create'
>
>
> So I'm a bit confused about 'quantity'. I've used it in another method
> in the line_item.rb and it worked (much to my surprise) but it doesn't
> work in this new method I'm writing.
>
> I really am an absolute beginner so I'm really just guessing most of the
> time. Any suggestions or hints would be most appreciated.
>
> thanks in advance for your patience.
>
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