From: Zach Dennis <zdennis@...>
Date: 2003-12-18T13:15:26+09:00
Subject: Re: Configuration Files

John,

What type of environment would you think something like this would apply to?

I dont' know what the "previous concept" was and it is hard for me to get a
good grasp in your post. Please help me understand. =) Thanks,

Zach

-----Original Message-----
From: John W. Long [mailto:ws@johnwlong.com]
Sent: Wednesday, December 17, 2003 11:01 PM
To: ruby-talk ML
Subject: Configuration Files


A while back someone submitted some code to this list for evaluating
Configuration files in the style of:

% cat test.config
editor.spacespertab = 4
toolbar.visible = true
statusbar.visible = false
.. . .

One of the great things about their code was that it enabled you to use ruby
code within your configuration file so you could do things like this:

%cat test2.config
timer.alarm = 30 * 60 # set the timer to go off in 30 min

Their implementation was pretty simple. Mainly they created a hash,
splitting each line on /=/, and evaled the right side and stored the result
in the hash with a key of the left side.

I like this concept, but I wanted a better implementation. So I set to work
and created the attached files. The attached now enables you to do this:

%cat myprog.rb
require 'config'

$conf = Config.new

# set up the default values and configuration structure:
$conf.define %{
    editor.spacespertab = 8
    toolbar.visible = false
    toolbar.caption = "Tools"
    statusbar.visible = true
    copyright = "Copyright &copy; 2003, John W. Long"
}

$conf.read File.new('test.config', 'r').read

# you can even read multi line ruby snippets:
$conf.read %{
    copyright = "Copyright &copy; 2003, John W. Long
                  All Rights Reserved"
    alarm = 30 * 60 #seconds
}

# now for getting the values, note the object hierarchy
toolbar.caption = $conf.toolbar.caption.value
toolbar.show if $conf.toolbar.visible.value
aboutbox.copyright = $conf.copyright.value
.. . .

You get the idea.

A couple of advantages that this has over the previous concept:
-- You define the default values and create the config structure at the same
time
-- Because you define a config structure if someone makes a typo in the
config file misspelling "toolbar" as "tolbar" an error will be thrown
(eventually it will even tell you what line the error was on)
-- You access the values from the config file in almost the same way that
they are written into the config file on your Config object

I didn't attach the unit tests of this version because the code still
relatively crude. Once I get things worked out a bit I may post it on
RubyForge.

Feedback is appreciated.

___________________
John Long
www.wiseheartdesign.com