From: Robert Klemme <shortcutter@...>
Date: 2007-05-26T17:05:13+09:00
Subject: Re: Global Array?

On 26.05.2007 05:32, Dan Zwell wrote:
> Sy Ys wrote:
>> I've got a class which calls itself several times (recursive). While
>> this class is calling itself, I want it to be appending a global array (
>> << ). I can't figure out how to make the array itself global, so for now
>> each time the class calls itself, it creates the array anew again. Help?
>>
> 
> class Klass
>   def recurse
>     $klasses = Array.new  unless \
>       global_variables.include?("$klasses") and $klasses.is_a?(Array)
>     unless $klasses.size > 40
>       k = Klass.new
>       $klasses << k
>       k.recurse
>     end
>   end
> end
> 
> Note that I found the "and $klasses.is_a?(Array)" bit necessary because 
> the parser seems to initialize the global array $klasses when it first 
> comes across the word. Might I suggest using a class level variable 
> instead (@@klasses)? It seems appropriate. They are "almost global."

No, rather use a class instance variable.  But even that has problems 
because it is not thread safe.

The solution really depends on the problem to solve.  Maybe it's a 
global variable, maybe it's a thread local, maybe it's a parameter like in

def foo(x=[])
   if ...
     # recursion
     foo(x)
   else
     # termination
   end
end

... or maybe it's even another class with an instance variable, i.e. 
factor out the recursive functionality into another class.

It all depends...

	robert