From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-04-23T23:22:27+09:00
Subject: Re: Class variable confusion

On Thu, Apr 23, 2009 at 4:01 PM, Keith Salisbury
<keithsalisbury@gmail.com> wrote:
> Or more simply, i would like this to update the variable @greeting, when
> i call Keith.learn_french:
>
> module Keith
>  def self.greeting
>    @greeting ||= "hello"
>  end
>  def self.greeting=(value)
>    puts "updating knowledge"
>    @greeting = value
>  end
>  def self.speak
>    puts greeting
>  end
>  def self.learn_french
>    learn_language(greeting, "bonjour")

Here, you are calling the greeting method (which returns "hello")

>  end
>  def self.learn_language(prop, value)
>    prop = value

Here you are reassigning a local variable, which goes out of scope
when the method ends.
Try this:


jesus@jesus-laptop:~/temp/ruby$ ruby class_variables.rb
hello
bonjour

jesus@jesus-laptop:~/temp/ruby$ cat class_variables.rb
module Keith
 def self.greeting
   @greeting ||= "hello"
 end
 def self.greeting=(value)
   puts "updating knowledge"
   @greeting = value
 end
 def self.speak
   puts greeting
 end
 def self.learn_french
   learn_language(:@greeting, "bonjour")
 end
 def self.learn_language(prop, value)
   instance_variable_set(prop, value)
 end
end

Keith.speak
Keith.learn_french
Keith.speak


or if you want to call the self.greeting= method, try this variation:

def self.learn_french
   learn_language(:greeting, "bonjour")
 end
 def self.learn_language(prop, value)
   send("#{prop}=", value)
 end

Hope this helps,

Jesus.