From: Jeremy Bopp <jeremy@...>
Date: 2010-10-06T04:31:42+09:00
Subject: Re: Calling a method with an instance

On 10/5/2010 1:59 PM, Paul Roche wrote:
> Hi. I'm playing around with creating methods and then creating an
> instance that calls the instance. Here's my code.....
> 
> 
> class Discount
> attr_accessor :amount, :discount
> 
>  def initialize(am, dis)
> @amount = am
> @discount = dis
> 
> end
> 
> 
> def self.discount_amount(amt, disc)
> newamount = amt - disc
> end
> 
> end
> 
> 
> dis1 = Discount.new(100, 20)
> 
> dis1.discount_amount(amount, discount)
> 
> 
> The error I get is......
> 
> discount.rb:25:in `<main>': undefined local variable or method `amount'
> for main
> :Object (NameError)
> 
> 
> What is the best way to call a method with an instance?
> Thanks

There are a couple issues.  First of all, you are trying to use two
variables (amount and discount) without giving them any values, in other
words without defining them.  That's why you get the error "undefined
local variable or method `amount'".  Perhaps you mean to use dis1.amount
and dis1.discount instead.

Once you clear that hurdle, you'll find you also declared the
discount_amount method as a class method on Discount, not an instance
method.  However, you go on to call the method as an instance method of
dis1.  I think the corrected code would be as follows:

Discount.discount_amount(dis1.amount, dis1.discount)

-Jeremy