From: "David A. Black" <dblack@...>
Date: 2008-03-14T12:27:11+09:00
Subject: Re: Naming ruby class attribute and methods

Hi --

On Fri, 14 Mar 2008, Demonic Software wrote:

> Hello,
>
> Is there a way to name all the methods and attributes/ class instantiated
> variables that have been created?  For example, from the class below, I
> would like to get all the variables instantiated from the initialize and
> example methods, and then I would also like to be able to get the method
> names.
>
>
> #pseudo code, not sure if it really runs
> class Foo
>  def initialize()
>     @thestring = ''
>     @haha = "HA HA HAA!"
>     @var = "I am a variable"
>  end
>  def example(arg)
>     @arg = arg
>     @thestring = "#{@haha} #{@var}: #{arg}"
>  end
>  def thestring
>     @thestring
>  end
> end
>
>
> So is there a way to extract ["thestring", "var", "haha", "arg"] for the
> variable names and then  ["initialize", "example", "thestring"] for the
> method names.  I can see how I would do it with regular expressions and
> ruby2ruby, but I was wondering if there was another way of extracting the
> information.  Thanks in advance.

You can get method and instance variable names. An "attribute" is
really a kind of virtual construct, composed of methods and (usually)
instance variables, so it doesn't appear as a separate thing when you
do introspective stuff on the object. The main time "attribute" exists
is when you create them; after that, they're just methods (though one
is of course free to continue to call them attributes).

Foo.instance_methods(false) will give you all the instance methods
defined in Foo. (The rather cryptic "false" means: don't include
methods created higher in the ancestry.) To get the instance variables
you have to instantiate the class, run the methods that create them,
and then call the #instance_variables method. (Just defining methods
with i. vars inside them doesn't create the i. vars.)


David

-- 
Upcoming Rails training from David A. Black and Ruby Power and Light:
   ADVANCING WITH RAILS, April 14-17 2008, New York City
   CORE RAILS, June 24-27 2008, London (Skills Matter)
See http://www.rubypal.com for details. Berlin dates coming soon!