Error: You have a nil object when you didn't expect it!

Hi everyone,

Very new to rails and while following the book: Beginning Ruby on
Rails E-Commerce", I’m trying ti implement a cart, but the cart
doesn’t appear on the html page at all. The code for the cart in app/
views/layouts/application.rhtml:

<% if @cart %>

<%= render :partial => "cart/cart" %>
<%= drop_receiving_element("shopping_cart", :url => { :controller => "cart", :action => "add" }) %> <% end %>

If I take out the if @cart, I get this error:

You have a nil object when you didn’t expect it!
The error occurred while evaluating nil.cart_items

Extracted source (around line #7):

4:
5:

Your Shopping Cart


6:

    7: <% for item in @cart.cart_items %>
    8:

  • 9: <%= render :partial => “cart/item”, :object => item %>
    10:
  • This code appears on app/views/cart/_cart.rhtml

    Please help. Anyone?

    TIA,
    Elle

You have to declare the @cart variable in the controller.

On Sep 2, 12:33 am, “Thomas W.” [email protected]
wrote:

You have to declare the @cart variable in the controller.

Thanks for the quick reply. Here is my cart_controller.rb:

class CartController < ApplicationController
before_filter :initialize_cart

def add
params[:id].gsub!(/product_/, “”)
@product = Product.find(params[:id])

if request.xhr?
  @item = @cart.add(params[:id])
  flash.now[:cart_notice] = "Added <em>#{@item.product.title}</

em>"
render :action => “add_with_ajax”
elsif request.post?
@item = @cart.add(params[:id])
flash[:cart_notice] = “Added #{@item.product.title}
redirect_to :controller => “catalog”
else
render
end
end

and my cart.rb model:

class Cart < ActiveRecord::Base
has_many :cart_items
has_many :products, :through => :cart_items

def add(product_id)
items = cart_items.find_all_by_product_id(product_id)
product = Product.find(product_id)
if items.size < 1
ci = cart_items.create(:product_id => product_id,
:amount => 1,
:price => product.price)
else
ci = items.first
ci.update_attribute(:amount, ci.amount + 1)
end
ci
end

and my cart_item.rb model:

class CartItem < ActiveRecord::Base
belongs_to :cart
belongs_to :product
end

What am I doing wrong?

TIA,
Elle

On Sep 2, 6:28 am, elle [email protected] wrote:

def add
flash[:cart_notice] = “Added #removed_email_address@domain.invalid}
has_many :cart_items
ci = items.first
belongs_to :product
end

What am I doing wrong?

TIA,
Elle

Hi Elle,

What code do you have for the initialize_cart method in the
CartController?

Cheers,
Louis.

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