From: Brian Candler <b.candler@...>
Date: 2008-10-29T05:31:40+09:00
Subject: Re: Proper way to define a subclass within parent file?

Scott Strattner wrote:
>> Another possibility, if the values in the instance variables shouldn't 
>> change
>> is to use constants:
> 
> I originally had methods to modify these class variables, but I just 
> tried using constants, and that worked. So I will probably create a 
> subclass for every kind of VLAN encountered (which will then define the 
> constant values for that particular subclass).

Note: when referring to constant Foo, use self.class::Foo in a subclass 
if you want dynamic lookup, otherwise Foo will statically be resolved to 
the one in the parent.

class Bar
  Foo = 1
  def test1
    Foo               # always refers to Bar::Foo, even in a subclass
  end
  def test2
    self.class::Foo
  end
end

class Baz < Bar
  Foo = 2
end

p Bar.new.test1 # prints 1
p Baz.new.test1 # prints 1
p Bar.new.test2 # prints 1
p Baz.new.test2 # prints 2
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