From: John Carter <john.carter@...>
Date: 2006-08-09T06:11:43+09:00
Subject: Re: Global variables considered harmful?

On Wed, 9 Aug 2006, darren kirby wrote:

> I have a Ruby script here that acts like a regular Unix program, including
> accepting a large number of command-line options/arguments. After processing
> some  are simple flags (ie: nil or 1) and some are text/numeric arguments.
> Not all are required, and some must be initialized with a default value. I
> have currently implemented them as globals, as their values are needed
> anywhere in my script, from classes to functions to top-level flow control
> code...

I tend to parcel such things up into a Context object. Sort of like...

class MyProgContext

   def initialize( argv)
      parse_args( argv)
      sanity_check
   end

   def print_help_and_exit( plain="Usage:-")
     puts "
#{plaint}

myprog [options] arg1 arg2

Description

"
     exit( 1)
   end

end

context = MyProgContext.new( ARGV)

....

Advantages :-
  * Collects all the stuff neatly into a class.
  * Allows me to enforce invariants (ie. sanity check options / arguments for
    mutual compatibility / sanity.
  * Easy to unit test the ARGV parsing logic.





John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand

Carter's Clarification of Murphy's Law.

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From this principle, all of life and physics may be deduced.