From: Jeremy Bopp <jeremy@...>
Date: 2010-10-06T04:46:50+09:00
Subject: Re: Calling a method with an instance

On 10/5/2010 2:32 PM, Paul Roche wrote:
> Jedrin wrote:
>> On Oct 5, 3:20�pm, Jedrin <jrubia...@gmail.com> wrote:
>>>> �def initialize(am, dis)
>>>
>>>> What is the best way to call a method with an instance?
>>>> Thanks
>>>> --
>>>> Posted viahttp://www.ruby-forum.com/.
>>>
>>> I think u want:
>>> dis1.discount_amount(dis1.amount, discount)
>>
>> this works, but not sure if this approach is most sensible
>>
>> dis1.discount_amount(dis1.amount, dis1.discount)
> 
> Thanks for this. What is the best way to go about dealing with a method 
> such as this that has two parameters?

I think the comment about sensibility regards the passing of an object's
internal values to one of the object's own methods.  Assuming you
redefine the discount_amount method as an instance method, there is no
need to pass in these values since they will be available to the method
as @amount and @discount:

class Discount
  attr_accessor :amount, :discount

  def initialize(amount, discount)
    @amount = amount
    @discount = discount
  end

  # defined discount_amount as an instance method rather than a
  # class method
  def discount_amount
    @amount - @discount
  end
end

dis1 = Discount.new(100, 20)
dis1.discount_amount        # => 80


-Jeremy