Question

I am following the Agile Web Development book tutorial with some small changes, halfway through Chapter 12 on Check Out.

I am getting the following error:

NoMethodError (undefined method `price=' for #<LineItem:0x00000103a0de18>):
app/models/cart.rb:11:in `add_deal'
app/controllers/line_items_controller.rb:45:in `create'

Here is my cart model:

class Cart < ActiveRecord::Base
# attr_accessible :title, :body
has_many :line_items, dependent: :destroy

def add_deal(deal_id)
  current_item = line_items.find_by_deal_id(deal_id)
  if current_item
    current_item.quantity += 1
  else
    current_item = line_items.build(deal_id: deal_id)
    current_item.price = current_item.deal.price
  end
current_item
end
def total_price
  line_items.to_a.sum { |item| item.total_price }
end
end

Here is my create action in line_items_controller with the relevant line 45 where it freezes:

def create
  @cart = current_cart
  deal = Deal.find(params[:deal_id])
  @line_item = @cart.add_deal(deal.id)

My line item model:

class LineItem < ActiveRecord::Base
attr_accessible :cart_id, :deal_id, :quantity
belongs_to :order
belongs_to :deal
belongs_to :cart

def total_price
  deal.price * quantity
end
end

Here is my deal model:

class Deal < ActiveRecord::Base
  attr_accessible :description, :expiration, :featured, :image_url, :inventory, :price, :sold, :title, :value, :deal_id

has_many :line_items

before_destroy :ensure_not_referenced_by_any_line_item

validates :price, numericality: {greater_than_or_equal_to: 0.01}
validates :title, uniqueness: true
validates :title, :description, :image_url, presence: true

private

# ensure that there are no line items referencing this product
def ensure_not_referenced_by_any_line_item
  if line_items.empty?
    return true
  else
    errors.add(:base, 'Line Items present')
    return false
  end
end
end

When I tried using the console, item.deal.price works just fine but not item.price.

In the line_item model, I tried attr_accessible :price but it did fix anything.

I checked my code vs the book and I can’t tell any significant difference at all.

One idea is to set a database field for price for LineItems but the book doesn’t do that and it violates the DRY principle.

Any help would be greatly appreciated as I’ve stared at the source code for hours and can’t find anything wrong. Thanks.

Answer 1

You were distracted during reading the book. LineItem model does contain the price field. This totally complies with DRY principle, as there is a possibility of changing a price of a Product in the future and LineItem model shows as a history of deals.