Fun with blocks, procs and lambdas.

bob_explorer.rb

class Adventurer
  attr_accessor :name, :location

  def initialize(name, location = "Edge of Forest")
    @name = name
    @location = location
  end

  def move(&block)
    block.call(self)
  end
end

class Forest
  attr_accessor :areas

  def initialize
    @areas = {
      "Edge of Forest" => Proc.new do |adventurer, callback|
        puts "#{adventurer.name} is standing at the edge of the forest."
        callback.call("birds singing") if callback
      end,
      "Deep in Forest" => Proc.new do |adventurer, callback|
        puts "#{adventurer.name} is lost deep within the forest."
        callback.call("a rustling in the bushes") if callback
      end,
      "Forest Clearing" => Proc.new do |adventurer, callback|
        puts "#{adventurer.name} found a clearing with a serene pond."
        callback.call("a fish jumping in the pond") if callback
      end
    }
  end

  def explore(area, adventurer, &callback)
    if @areas.key?(area)
      @areas[area].call(adventurer, callback)
    else
      lambda { |adventurer| puts "#{adventurer.name} wandered into an unknown part of the forest." }.call(adventurer)
    end
  end
end

def observe(event)
  puts "While exploring, you observe: #{event}"
end

forest = Forest.new
bob = Adventurer.new("Bob")

bob.move do |adventurer|
  adventurer.location = "Deep in Forest"
end

forest.explore(bob.location, bob) do |event|
  observe(event)
end

bob.move do |adventurer|
  adventurer.location = "Forest Clearing"
end

forest.explore(bob.location, bob) do |event|
  observe(event)
end

bob.move do |adventurer|
  adventurer.location = "Dark Cave"
end

forest.explore(bob.location, bob) do |event|
  observe(event)
end

output.txt

Bob is lost deep within the forest.
While exploring, you observe: a rustling in the bushes
Bob found a clearing with a serene pond.
While exploring, you observe: a fish jumping in the pond
Bob wandered into an unknown part of the forest.