Errors ... errors and errors

Rails
1

I bought the second edition of the ruby on rails, it seems to work fine
now, did some adjustments to the code. But now I get a second error and
I want to learn to understand to fix them myself. So here is the error.

ArgumentError in StoreController#add_to_cart
wrong number of arguments (1 for 0)
#{RAILS_ROOT}/app/models/cart.rb:15:in initialize' #{RAILS_ROOT}/app/models/cart.rb:15:inadd_product’
#{RAILS_ROOT}/app/controllers/store_controller.rb:19:in `add_to_cart’
-e:4

Now, it says as far as I understand it, that it should need 0 arguments
instead of 1. But that should be quite impossible, beacause the cart.rb
has a def add_product(product) as we shall see later. I do not
understand why it gives me that error. Here is the store_controller.rb:

[CODE]
class StoreController < ApplicationController

def index
@products = Product.find_products_for_sale
#creates an instance variable that holds a list of all the
#products in order to make it available to the code in the view
#that will display the table
#find_products_for_sale() IS DEFINED IN product.rb
end

def add_to_cart
@cart = find_cart #we use find_cart method to find (or create)
#a cart in this session
@product = Product.find(params[:id]) #we use the params object
#to get the id parameter
#from the request and then
#call Product model to find
#the product with that id.
@cart.add_product(@product) #add this product to the cart
end
private
def find_cart
unless session[:cart] #if there is no cart in sesssion add one
session[:cart] = Cart.new #add a new one
end
session[:cart] #return existing or new cart
end
end

[CODE]

Also here is the cart.rb

[CODE]
class Cart
include Reloadable

attr_reader :items

def initialize
@items = []
end

def add_product(product)
existing_product = @items.find {|item| item.product == product}
if existing_product
existing_product.increment_quantity
else
@items << Cart.new(product)
end
end
end

[CODE]

And here is the cart_item.rb

[CODE]
class CartItem
include Reloadable
attr_reader :product, :quantity

def initialize(product)
@product = product
@quantity = 1
end

def increment_quantity
@quantity += 1
end

def title
@product.title
end

def price
@product.price * @quantity
end

end

[CODE]

2

Hi,

it’s the add_to_cart method (not add_product(argument)) that you are
calling with one argument.

This method of your store controller takes no argument so the ruby
interpreter is complaining.

Cheers,
Jan

3

Where do I call this add_to_cart method without one argument? I only
call it in index.rhtml, otherwise I see not.

4

Jan P. wrote:

Hi,

it’s the add_to_cart method (not add_product(argument)) that you are
calling with one argument.

This method of your store controller takes no argument so the ruby
interpreter is complaining.

Cheers,
Jan

Understood, thanks a lot. Here is the code for the index.rhtml. The “:id
=> product” can be asumed to be the first parameter of the function? How
can I fix this so it will work?

[CODE]

Your Pragmatic Catalog

<% for product in @products -%>



<%= h(product.title) %>


<%= product.description %>

Pret: <%= product.price %>
RON


<%= button_to “Add to cart”, :action => :add_to_cart, :id =>
product %>

<% end %>

[CODE]

5

Jan P. wrote:

Hi,

sorry - seems as if the problem happens on line 15 of the Cart class:
@items
<< Cart.new(product)

You’re initializing a new Cart with the argument product, but haven’t
got an
initialize method that takes a product as an argument.

Cheers,
Jan

new(attributes = nil) {|self if block_given?| …}
New objects can be instantiated as either empty (pass no construction
parameter) or pre-set with attributes but not yet saved (pass a hash
with key names matching the associated table column names). In both
instances, valid attribute keys are determined by the column names of
the associated table â?? hence you canâ??t have attributes that arenâ??t part
of the table columns.

It can support attributes as far as I see her the new method. How would
you write the application so it works?

6

Hi,

sorry - seems as if the problem happens on line 15 of the Cart class:
@items
<< Cart.new(product)

You’re initializing a new Cart with the argument product, but haven’t
got an
initialize method that takes a product as an argument.

Cheers,
Jan

7

Finally, I replace Cart.new(product) with CartItem.new(product). Since
the Class Cart does NOT support another argument, of course it gave me
an error. But CartItem DOES support a new argument … so it works.

[CODE]
class CartItem
include Reloadable
attr_reader :product, :quantity

def initialize(product)
@product = product
@quantity = 1
end

def increment_quantity
@quantity += 1
end

def title
@product.title
end

def price
@product.price * @quantity
end

end

[CODE]