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

rubyonrails-talk
1

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 %> <div id="shopping_cart">   <%= render :partial => "cart/cart" %> </div> <%= 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: <h3>Your Shopping Cart</h3> 6: <ul> 7: <% for item in @cart.cart_items %> 8: <li id="cart_item_<%= item.product.id %>"> 9: <%= render :partial => "cart/item", :object => item %> 10: </li>

This code appears on app/views/cart/_cart.rhtml

Please help. Anyone?

TIA, Elle

2

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

3

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}</

"

      render :action => "add_with_ajax"     elsif request.post?       @item = @cart.add(params[:id])       flash[:cart_notice] = "Added <em>#{@item.product.title}</em>"       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

4

Hi Elle,

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

Cheers, Louis.