From: Trans <transfire@...>
Date: 2007-01-22T02:52:58+09:00
Subject: Re: module global variables


Stefano Zacchiroli wrote:
> Is there a way to define per-module global variables? My best
> approximation is the following
>
>   module Foo
>     @@x = 0
>     def do_something_on_x
>       @@x = ...
>     end
>     def x
>       @@x
>     end
>   end
>
> The drawbacks are that I haven't found anything similar to
> attr_reader/writer/... for instance variables.
>
> If interested in the real use case here it is: I've defined a module
> which include a set of common functionalities which need to deliver
> messages with a given verbosity. I want to avoid to pass the verbosity
> configuration to all the involved class and methods but I want to avoid
> to use a global $verbosity variable since the setting should be limited
> to all the functionalities implemented by my module.
>
> Here is how I'm using the verbosity setting:
>
>   module Foo
>     @@verbosity = 0
>     def incr_verbosity
>       @@verbosity += 1
>     end
>     def verbosity
>       @@verbosity
>     end
>   end
>
> I would love to write something like
>
>   module Foo
>     @@verbosity = 0
>     module_attr_reader :verbosity
>     def incr_verbosity
>       @@verbosity += 1
>     end
>   end
> 
> Am I using the wrong tool for my end?

Try a constant.

T.