From: Rob Biedenharn <rob@...>
Date: 2012-08-25T04:45:34+09:00
Subject: Re: learning by doing part 2 - tc game

On Aug 24, 2012, at 3:26 PM, Sebastjan H. wrote:

> Once again, I turn to you for your wisdom:)
> 
> Why this works:
> -----------------------------------------
> class Depo
> attr_accessor :test
> 
> def initialize(test)
> @test = test
> end
> 
>  def test()
>  @test
>  end
> end
> 
> bla = Depo.new("blahdsd")
> 
> def defin (bla)
> if defined? test
> puts "#{bla.test}"
> end
> end
> 
> defin(bla)
> ------------------------------------------
> 
> And this doesn't:
> ------------------------------------------
> def effect_output(card)
>  if defined? attack
>    puts "#{card.name.capitalize} hits with #{card.attack}."
>  elsif defined? heal
>    puts "#{card.name.capitalize} heals for #{card.heal}."
>  end
> end
> ------------------------------------------
> The card is a DRAGON class object with method attack defined. It has the 
> attr_accessor as well as initialize method defined. I don't even get an 
> error. Nothing gets putsed.
> 
> If I use
> 
> if defined? :attack
> 
> then I get the message that attack is an undefined method for class 
> HEAL.
> 
> ???

You don't want defined? here, you want respond_to? as in:

if card.respond_to?(:attack)
  # do something involving card.attack
end

-Rob