testruleby.rb

require 'ruleby'
include Ruleby

class CoffeeOperationRulebook < Rulebook
  # Note the rules do not have to be in order
  def rules
    rule [Machine, :m, m.status == :GRINDING] do |v, e|
      puts "Grinding complete, puring coffee"
      v[:m].status = :POURING
      e.modify v[:m]
    end

    rule [Machine, :m, m.status == :READY] do |v, e|
      puts "Machine Ready, griding coffee"
      v[:m].status = :GRINDING
      e.modify v[:m]
    end

    rule [Machine, :m, m.status == :POURING] do |v, e|
      puts "Pouring complete, stop machine"
      v[:m].status = :READY
    end
  end
end

class Machine
  attr_accessor :status
end

engine :coffee_operation do |e|
  m = Machine.new.tap { |m| m.status = :READY }
  CoffeeOperationRulebook.new(e).rules
  e.assert m
  e.match
end%