Rails Undefined method error showing up out of the blue

Question

I am making an app with a shopping cart and have had the shopping cart working for weeks until today when I randomly started to get the following error:

undefined method `title' for nil:NilClass

Extracted source (around line #20):

            <%= link_to product.title, product %>

                <p><%= number_to_currency(product.price, :unit => '$') %></p>
                <p>Quantity: <%= quantity %></p>

I can not figure out why this started to show up and how to fix it.

Here is my code: cart controller:

class CartController < ApplicationController

 def add
    id = params[:id]
      if session[:cart] then
         cart = session[:cart]
      else
        session[:cart] = {}
        cart = session[:cart]
      end

      if cart[id] then
          cart[id] = cart[id] + 1
      else
          cart[id] = 1
      end
    redirect_to :action => :index  end
       def clearCart
      session[:cart] = nil
      redirect_to :action => :index   end
       def index
    if session[:cart] then
      @cart = session[:cart]
    else
      @cart = {}
    end   end


end

cart/index.html.erb:

<div class="shoping-cart">
<h1>Your Cart</h1>

<% if  @cart.empty? %>
    <p>Your cart is currently empty</p>
<% else %>
    <%= link_to 'Empty Cart', cart_clear_path %>
<% end %>

<br><br><br>

<% total = 0 %>
<div class="list">
<ul>
<% @cart.each do | id, quantity | %>
    <% product = Product.find_by_id(id)  %>

        <li>

            <%= link_to product.title, product %>

            <p><%= number_to_currency(product.price, :unit => '$') %></p>
            <p>Quantity: <%= quantity %></p>

        </li>
        <% total += quantity * product.price %>

<% end %>

<br><br><br>


<p><p><%= number_to_currency(total, :unit => '$') %></p></p>
</ul>
</div>
<% link_to 'pay now',  new_charge_path %>

</div>

Routes:

 get '/cart' => 'cart#index'
  get '/cart/clear' => 'cart#clearCart'
  get '/cart/:id' => 'cart#add'

mr_sudaca · Accepted Answer · 2016-05-09 02:27:39Z

1

you need to avoid doing queries inside your views, but, if you want to keep that Product.find_by_id then you can add a guard class there:

<% @cart.each do | id, quantity | %>
 <% product = Product.find_by_id(id)  %>
  <% if product %>
    <li>

        <%= link_to product.title, product %>

        <p><%= number_to_currency(product.price, :unit => '$') %></p>
        <p>Quantity: <%= quantity %></p>

    </li>
    <% total += quantity * product.price %>
   <% end %>
<% end %>

edited May 9, 2016 at 2:27

answered May 8, 2016 at 1:09

mr_sudaca

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