DSLs

context.md

From a question about DSLs.

See:

• http://www.ruby-forum.com/topic/4410760

The code in the Adventure::Room class could be made a little cleaner using a gem like fattr

dsl.rb

class Adventure
  attr_reader \
    :current_room,
    :rooms

  class Room
    attr_accessor \
      :exits,
      :long,
      :short
      
    def initialize( short , long , exits )
      @short = short
      @long = long
      @exits = exits
    end
    
    def long( val = false )
      if val
        self.long = val
      else
        self.long
      end
    end
    
    def short( val = false )
      if val
        self.short = val
      else
        self.short
      end
    end
        
    def door(direction, destination, &block)
      if exits.has_key?( direction )
        puts "Error: Room #{@current_room} already has an exit defined in #{direction}"
      else
        exits[ direction ] = {:where => destination, :condition => block_given? ? block : true}
      end
    end
  end
  
  def initialize
    @rooms = Hash.new
    @current_room = nil
  end

  def room(reference, &block)
    @current_room =
      if @rooms.has_key?(reference)
        puts "Error: Room #{reference} has already been defined"
        @rooms[ reference ]
      else
        @rooms[ reference ] = Room.new '' , '' , Hash.new
      end

    @current_room.instance_eval( &block ) if block_given?
  end
end

class Object
  def adventure(&block)
    a = Adventure.new
    a.instance_eval( &block ) if block_given?
  end
end

adventure do
  room :cave do
    short "You are in a large cave"
    long "You are in a very large cave"
    door :west, :another_cave
    door :east, :exit do
      if player.has_item(:key)
        true
      else
        false
      end
    end
  end

  room :another_cave do
    short "A cave"
    long "Oh great ... another cave"
    door :east, :cave
  end

  room :exit do
    short "Freedom"
    long "Freeeeeeeeeeedom!!!!!!"
    door :west, :cave
  end

  require 'pp'
  pp @rooms
end