From: Steve Tuckner <STUCKNER@...>
Date: 2002-08-08T04:10:34+09:00
Subject: RE: Class hierarchy... for data

I have wanted to do what you talked about. Here is my solution. Please ruby
experts make it better if possible :->

class Object
	def Object.parent_field(*names)
		names.each do |name|
	    	module_eval <<-"end;"
				def #{name}
					if type.instance_methods.include?("#{name}_") then
						send("#{name}_")
					elsif defined?(@#{name}) then
						@#{name}
					else
						@parent.#{name}
					end
				end

				def #{name}=(value)
					if type.instance_methods.include?("#{name}_=") then
						send("#{name}_=", value)
					else
						@#{name} = value
					end
				end
		 	end;
		 end
	end
end

class A
	parent_field :x, :y, :z

	def initialize(parent)
		@parent = parent
	end

	def x_=(value)
		@x = value * 2
	end
end

a = A.new(nil)
b = A.new(a)
c = A.new(b)

a.x = 1
a.y = 2
a.z = 3
b.y = 11
b.z = 12
c.z = 21

print "#{a.x}, #{a.y}, #{a.z}\n"
print "#{b.x}, #{b.y}, #{b.z}\n"
print "#{c.x}, #{c.y}, #{c.z}\n"

Steve Tuckner

-----Original Message-----
From: Tom Gilbert [mailto:gilbertt@fs.tomsflat]On Behalf Of Tom Gilbert
Sent: Wednesday, August 07, 2002 12:47 PM
To: ruby-talk ML
Subject: Re: Class hierarchy... for data


* Gavin Sinclair (gsinclair@soyabean.com.au) wrote:
> > Anyone got anything similar? Or maybe some suggestions?
>
> Keep going; you're nearly there.

Heh. Just hoping I was missing a nicer way to do it - because once I've
implemented all the enumerable and hash methods I'll want this thing to
have it's going to be a fairly fat class :)

Thanks for the feedback.

Tom.
--
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   /V\    | Tom Gilbert, London, England | http://linuxbrit.co.uk |
 /(   )\  | Open Source/UNIX consultant  | tom@linuxbrit.co.uk    |
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