From: Alexis <Alexis.Lee@...>
Date: 2001-11-25T13:25:46+09:00
Subject: [ruby-talk:26421] New member, project(s) and questions

Hi,
An announcement and a couple of questions.

To learn Ruby I've started to write a MUD. I have a neat command engine and
a threaded server working just fine.

I decided I wanted to store the world data in a relational database. However,
I wanted this to happen with as little manual admin as possible. Hence I'm
defining an abstract class DBObj which supports get(id), put() (which updates
the DB record) and rel() (which doesn't). Yes, this means caretaking on
objects, but I have lots of threads so it needs to be done anyway.

Within DBObj I need to be able to find out what types the fields are. Right
now I'm trying to do this by asking descendants to have defaults for all
fields except id in initialize(), and doing this:

class DBObj
  # Creates the DB table
  # Needs type info to declare column types correctly
  def DBObj.mktable
    obj = new(0)	# Doesn't work
    @@dbfields.each { |sym|
        case obj.__send__(sym)
        when Integer
          sql << sym.id2name << " int"
	    ...
	    end
	}
  end
end

Any suggestions for neater ways to obtain this type information?
Particularly since calling new from DBObj creates a DBObj, not an instance of
the class "#{name}" reports as I had hoped.
My current thought is to call Desc.new(0).mktable. That's very yuk though.

Last question, is there any way to use variable variables? Like:

class Boo
  def initialize
    @ab = "Hi"
    puts @("ab")
  end
end
Boo.new

If I could use this to generate a Class object (IE Class.new("Boo")) then it
would solve my reflection problem.

If anyone is interested in any of the code I mentioned, drop me a line.


Alexis
--
"Teachers open the door, but you must enter by yourself" - Chinese proverb
Attention.
The early bird gets the worm. The second mouse gets the cheese. - Jen Hopkins