police.rb

require 'alias_dci'

class Person
  include AliasDCI::DataObject
  
  def point(thing)
    p "As a #{dci_roles.last||'Regular Person'} I am using my finger to point at #{thing}"
  end
end


class TrafficGuidance
  include AliasDCI::Context
  
  role :policeman do
    def point(thing)
      p "As a #{dci_roles.last} I am using my police batton to point at #{thing}"
    end
  end

  def initialize(person)
    assign_named_roles(:policeman =>  person)
  end
  
  def guide_traffic_then_buy_a_donut
    in_context do
      policeman.point("Cars")
      BuyADonut.new(policeman).get_donut
    end
  end
end

class BuyADonut
  include AliasDCI::Context
  
  role :customer do
    contract :point
    
    def pay_for_donut
      p "As a #{dci_roles.last} I am paying for the donut"
    end
  end

  def initialize(person)
    assign_named_roles(:customer =>  person)
  end
  
  def get_donut
    in_context do
      customer.point("Tasty Chocolate Donut")
      customer.pay_for_donut
    end
  end
end

bob =  Person.new
bob.point("a cat")
TrafficGuidance.new(bob).guide_traffic_then_buy_a_donut


# >> "As a Regular Person I am using my finger to point at a cat"
# >> "As a TrafficGuidance::Policeman I am using my police batton to point at Cars"
# >> "As a BuyADonut::Customer I am using my finger to point at Tasty Chocolate Donut"
# >> "As a BuyADonut::Customer I am paying for the donut"