From: Brian Candler <b.candler@...>
Date: 2009-05-27T17:42:21+09:00
Subject: Re: How to access variables from within class definition

eggman2001 wrote:
> I've got something like:
> 
> @var = 'brown'

This is an instance variable of the top-level (main) object.

> class Foo < ActiveRecord::Base
>   set_table_name @var
> end

Now you're inside class Foo, @var is an instance variable of the Foo 
class object (sometimes called a "class instance variable", but it's 
just an instance variable like any other)

> However, as the code is right now, I'm not able to access @var from
> within the class definition. Can someone tell me how I can accomplish
> this?

(1) Horrible:

class Foo < ActiveRecord::Base
  set_table_name eval("@var", TOPLEVEL_BINDING)
end

(2) Much better to use a local variable:

var = 'brown'
Foo.set_table_name var

That should work unless set_table_name is a private method. If it is, 
then:

(3)
var = 'brown'
Foo.class_eval { set_table_name var }

You see that local variables propagate happily into blocks. It's only 
'class' and 'def' which start with a clean slate as far as local 
variables are concerned.
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