From: David Alan Black <dblack@...>
Date: 2002-04-01T08:22:34+09:00
Subject: Re: Detecting class variables....

Hi --

On Mon, 1 Apr 2002, Sean Chittenden wrote:

> > > I have a class that will have many objects and each object has a
> > > rather expensive regexp that I don't want to recompile every instance.
> > > I was hoping to do something similar to:
> > >
> > > if @@httpd_combined_entry_re.nil?
> > >   @@httpd_combined_entry_re = Regexp.new('some regexp string')
> > > end
> > >
> > >
> > > Without using Modules#class_variables, there anyway to see if the
> > > symbol for a class variable is populated?  -sc
> >
> > Could you get by with the ||= assignment idiom?
> >
> >   @@class_var ||= Regexp.new('...')
>
> Nope.
>
> :46:in `initialize': uninitialized class variable
> @@httpd_combined_entry_re in Logs::Httpd::Combined::Entry (NameError)

How about something like:

class Thing
  @@var = nil
  def initialize
    @@var ||= Regexp.new('...')
  end
end


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav