I am playing around with writing some DSLs to help me get more familier
with how they work and I have a couple of questions. First here's an
example of one I am playing with (based on the classic dungeon adventure
problem)
class Adventure
def initialize
@rooms = Hash.new
@current_room = nil
end
def room(reference, &block)
if @rooms.has_key?(reference)
puts "Error: Room #{reference} has already been defined"
else
@rooms[reference] = {:short => '', :long => '', :exits => Hash.new}
end
@current_room = reference
yield block
end
def short(text)
@rooms[@current_room][:short] = text
end
def long(text)
@rooms[@current_room][:long] = text
end
def door(direction, destination, &block)
if @rooms[@current_room][:exits].has_key?(direction)
puts "Error: Room #{@current_room} already has an exit defined in
#{direction}"
else
@rooms[@current_room][:exits][direction] = {:where => destination,
:condition => block_given? ? block : true}
end
end
end
class Object
def adventure(&block)
a = Adventure.new
a.instance_eval(&block)
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
Now this works just fine but a couple of things just don't seem right.
Notice the @current_room variable that is set in the room method and
referenced in short, long and door. This seems clunky - it is basically a
global variable to help tie things together. Is there some better way of
doing this? Perhaps by passing it as a parameter somehow.
Also is the yield at the bottom of the room method the right way to go or
should I be calling instance_eval or similar?
Also how do I stop, for example, the door method being called outside of
the room method? I have a solution where I set @current_room to nil after
the yield and then each method checks to see if it is set and if not it
errors. But again this seems to be quite a pain.
