Undefined local variable or method 'product' - ruby

Question

I am doing a task that requires me add some products together and give a 10% discount providing the total is above £60. I have done the following:
class Checkout
def initialize (rules)
#rules = rules
#cart = []
end
def scan (item)
if product == Product.find(item)
#cart << product.clone
#Clone preserves frozen state whereas .dup() doesn't if use would raise a
#NoMethodError
end
end
def total
#cart = #rules.apply #cart
end
def self.find item
[item]
end
co = Checkout.new(Promotional_Rules.new)
co.empty_cart
co.scan(1)
co.scan(2)
co.scan(3)
puts "Total price: #{co.total}"
puts
co.empty_cart
co.scan(1)
co.scan(3)
co.scan(1)
puts "Total price: #{co.total}"
puts
co.empty_cart
co.scan(1)
co.scan(2)
co.scan(1)
co.scan(3)
puts "Total price: #{co.total}"
puts
However when I run this in irb I get undefined variable or method product. Sounds a bit daft but this should work.

Answer 1

You're using one too many equal signs
def scan (item)
# if product == Product.find(item)
if product = Product.find(item) # <--- should be this
#cart << product.clone
#Clone preserves frozen state whereas .dup() doesn't if use would raise a
#NoMethodError
end
end
Of course, then you'll get a different error since find doesn't exist on Product yet... which I think you're trying to define here:
def self.find item # self should be changed to Product
[item]
end
Then you're going to get an error for apply not existing for Promotional_Rules ...
One of the best ways to debug these errors is follow the stack traces. So for the last error I get the following message:
test.rb:53:in `total': undefined method `apply' for #<Promotional_Rules:0x007f94f48bc7a8> (NoMethodError)
from test.rb:72:in `<main>'
That's basically saying that at line 53 you'll find apply hasn't been defined for #rules which is an instance of Promotional_Rules. Looking at the Promotional_Rules class you've clearly defined that method as apply_to_item and not apply. If you keep following and fixing the rabbit trails like this for stack traces you'll be able to debug your program with ease!