From: "John W. Long" <ws@...>
Date: 2003-12-18T13:01:10+09:00
Subject: Configuration Files

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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

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	name="cleanobject.rb"
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	filename="cleanobject.rb"

class CleanObject=0A=
	alias :__extend__ :extend=0A=
	alias :__instance_eval__ :instance_eval=0A=
	def initialize=0A=
		methods.each { |s|=0A=
			symbol =3D s.intern=0A=
			next if s =3D~ /^__.*__$/=0A=
			next if [:instance_eval].include?(symbol)=0A=
			instance_eval %{ undef :#{symbol.to_s} }=0A=
		}=0A=
		instance_eval %{ undef :instance_eval }=0A=
	end=0A=
end=0A=

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	name="config.rb"
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	filename="config.rb"

require "cleanobject"=0A=
=0A=
class Config=0A=
	module Node=0A=
		attr_accessor :__defining__, :__children__, :value=0A=
		def __defining__=3D(value)=0A=
			@__children__ ||=3D Hash.new=0A=
			@__children__.each{ |s, v|=0A=
				v.__defining__ =3D value=0A=
			}=0A=
			@__defining__ =3D value=0A=
		end=0A=
		def method_missing(symbol, *args)=0A=
			@__children__ ||=3D Hash.new=0A=
			if @__defining__ =0A=
				s =3D symbol.to_s=0A=
				s =3D $1 if s =3D~ /(.*)=3D$/=0A=
				__instance_eval__ <<-CODE=0A=
					def #{s}=3D(value)=0A=
						unless @__children__.has_key?(:#{s})=0A=
							n =3D CleanObject.new=0A=
							n.__extend__(Node)=0A=
							n.__defining__ =3D true=0A=
							@__children__[:#{s}] =3D n=0A=
						end=0A=
						@__children__[:#{s}].value =3D value=0A=
					end=0A=
					def #{s}=0A=
						unless @__children__.has_key?(:#{s})=0A=
							n =3D CleanObject.new=0A=
							n.__extend__(Node)=0A=
							n.__defining__ =3D true=0A=
							@__children__[:#{s}] =3D n=0A=
						end=0A=
						@__children__[:#{s}]=0A=
					end=0A=
				CODE=0A=
				__send__ symbol, *args=0A=
			else=0A=
				raise NoMethodError, "undefined method `#{symbol}'"=0A=
			end=0A=
		end=0A=
	end=0A=
	=0A=
	def initialize=0A=
		@root =3D CleanObject.new=0A=
		@root.__extend__(Node)=0A=
	end=0A=
	=0A=
	def define(object)=0A=
		@root.__defining__ =3D true=0A=
		@root.__instance_eval__(prep(object.to_s))=0A=
		@root.__defining__ =3D false=0A=
	end=0A=
	=0A=
	def read(object)=0A=
		@root.__instance_eval__(prep(object.to_s))=0A=
	end=0A=
=0A=
	def prep(string)=0A=
		code =3D ""=0A=
		string.each { |line|=0A=
			c =3D line.strip=0A=
			c =3D "self.#{c}" unless c =3D~ /^self\./ or c !~ /=3D/=0A=
			code << "#{c}\n"=0A=
		}=0A=
		code=0A=
	end=0A=
	=0A=
	def method_missing(symbol, *args)=0A=
		@root.__send__ symbol, *args=0A=
	end=0A=
end=0A=

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