From: Pit Capitain <pit@...>
Date: 2004-08-04T04:43:47+09:00
Subject: Re: Closure question

Fitzgerald,Greg schrieb:

> I'm trying to make a function act as a counter, but I can't seem to get
> it to work.  Here's what I've tried:
> 
> def count
>   counter = 1
>   def count
>     proc {counter += 1}.call
>   end
>   counter
> end
> 
> 
> I was hoping for this:
> count => 1
> count => 2
> count => 3
> 
> Instead, I got this:
> count => 1
> count => NoMethodError: undefined method '+' for nil:NilClass

Hi Greg,

the inner def creates a new scope, so you can't access the counter variable from 
  there. Using define_method, you can avoid creating a new scope:

def count
   counter = 1
   self.class.send :define_method, :count do counter += 1 end
   counter
end

p count # => 1
p count # => 2
p count # => 3

Regards,
Pit