police.rb

require 'alias_dci'

class Person
  include AliasDCI::DataObject

  def point(thing)
    p "I'm using my finger to point at #{thing}"
  end
end


class DonutStreetVendorAtBlackedOutTraficlight
  include AliasDCI::Context
  
  role :policeman do
    def point(thing)
      p "I'm using my police batton to point at #{thing}"
    end
  end
  
  role :customer do
    contract :point
    
    def pay_for_donut
      p "I am paying for the donut"
    end
  end

  def initialize(a_person, another_person)
    assign_named_roles(:policeman =>  a_person, :customer => another_person)
  end
  
  def guide_traffic_and_have_customer_buy_a_donut
    in_context do
      policeman.point("Cars")
      r_customer.point("a Donut") # have to use "r_rolename" as policeman implements #point.
    end
  end
end


bob =  Person.new

DonutStreetVendorAtBlackedOutTraficlight.new(bob, bob).guide_traffic_and_have_customer_buy_a_donut

# => nil
# >> "I'm using my police batton to point at Cars"
# >> "I'm using my finger to point at a Donut"