From: Daniel Schierbeck <daniel.schierbeck@...>
Date: 2005-11-28T07:27:28+09:00
Subject: Re: Object access heirarchies

Leslie Viljoen wrote:
> I often have this problem in my projects.
> 
> I have a bunch of classes to do various things in my program, but
> once instantiated they each need access to each other. For example,
> in the adventure game I am working on, I have a Parser object that
> needs to manipulate a Player, Map and Things in the map.
> 
> I normally do such things by passing objects around when initializing,
> like so:
> 
> parser = Parser(Player.new(World.new(Map.new, Things.new)))
> 
> That works, although it seems a little long winded - for the
> parser to modify a thing, it needs to set something like:
> player.world.thing["ball"].name = "bat"
> 
> Later, the Things needed access to the Map so I could set thing.location
> to a map.room object. So I changed thing.location to be a string --
> thing.location_name and made a function that could look up a location
> based on it's name: map["garden"].
> 
> What I want to know is: what's the best way? I had globals $player, 
> $world, $map
> earlier and that makes things a bit easier but it also makes me nervous
> (perhaps just because I have been anti-global-indoctrinated for 20 years 
> now)
> I'm still a bit vague on Modules. Any ideas?
> 
> Les

What about a single base class?

   class Game
     attr_reader :parser, :world, :map, :things, :player

     def initialize
       @parser = Parser.new(self)
       @world  = World.new(self)
       @map    = Map.new(self)
       @things = Things.new(self)
       @player = Player.new(self)
     end

     class World
       def initialize(game)
         @game = game
       end

       def map
         @game.map
       end

       # ....
     end

     # ....
   end


Cheers,
Daniel