From: "Mehr, Assaph (Assaph)" <assaph@...>
Date: 2004-04-01T12:43:42+09:00
Subject: Re: script loading question


> Woo hoo!  thanks much.  I could not find the info about
const_get(name). 
> Works like a champ!

If all you agents inherit from one base-class, you can use the
#inherited method of the base class to automatically initialize the
factory.
If you want to 'delete' the old definition of the class, you can use
Class.new (you will get warnings about constant redefinitions). This was
in a different thread a couple of days ago. Put this in the top of each
DerivedAgent definition.

So the script:

  class Agent
    @@factory = {}
    def Agent.inherited(newAgent)
      @@factory[newAgent.name] = newAgent
    end
    def Agent.get_agent(agent_name)
      @@factory[agent_name].new
    end
  end

  class AlphaAgent < Agent; end
  class BetaAgent  < Agent
    def foo
      'beta foo'
    end
    def bar
      'bar'
    end
  end


  puts Agent.get_agent('AlphaAgent').class
  puts Agent.get_agent('BetaAgent').foo

  # simulate reloading the beta agent file:
  BetaAgent = Class.new
  class BetaAgent < Agent
    def foo
      'new beta foo'
    end
  end

  puts Agent.get_agent('BetaAgent').foo
  puts Agent.get_agent('BetaAgent').bar

Produces:

>ruby inherited.rb
AlphaAgent
beta foo
new beta foo
inherited.rb:27: warning: already initialized constant BetaAgent
inherited.rb:28: warning: already initialized constant BetaAgent
inherited.rb:35: undefined method `bar' for #<BetaAgent:0x27863b8>
(NoMethodError)