From: Joel VanderWerf <vjoel@...>
Date: 2007-11-08T15:00:21+09:00
Subject: Re: alternate to case; generating a list of sub-classes

Phrogz wrote:
> class Foo
>   ALL = []
>   def initialize
>     ALL << self
>   end
> end
> 
> There's even some interesting benefits to the scoping, like:
> 
> # By inheriting the superclass's initialize,
> # Bar1 instances get put into Foo::ALL
> class Bar1 < Foo; end
> 
> # But I can totally branch on my own without worrying about
> # any class variable sort of nonsense
> class Bar2 < Foo
>   ALL = [] # separate from Foo::ALL
>   def initialize
>     ALL << self
>   end
> end
> 
> Thanks for that, Ara!
> 

Careful though, constant scoping is not dynamic:

class Foo
   def self.show_all
     p ALL
   end
end

3.times {Foo.new}
Foo.show_all   # [#<Foo:0x2ae5e8c>, #<Foo:0x2ae5e78>, #<Foo:0x2ae5e64>]

3.times {Bar2.new}
Bar2.show_all  # [#<Foo:0x2ae5e8c>, #<Foo:0x2ae5e78>, #<Foo:0x2ae5e64>]


Of course, you can get dynamic scoping, it's just easy to forget:

class Foo
   def self.show_all
     p self::ALL
   end
end

-- 
        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407