visitor_implementation.rb

# Each of the following classes visit the objects, doing something different
# each time.
class CarElementPrintVisitor
  def visit(subject)
    puts "Visiting: %s" % subject.class.to_s
  end
end

class CarElementDoVisitor
  def visit(subject)
    puts "Do some other visitation: %s" % subject.class.to_s
  end
end

c = Car.new
c.accept(CarElementPrintVisitor.new) # pass an object that will be visited
c.accept(CarElementDoVisitor.new)    # same here

# OUTPUT
# Visiting: Wheel
# Visiting: Wheel
# Visiting: Wheel
# Visiting: Wheel
# Visiting: Body
# Visiting: Engine
# Visiting: Car
# Do some other visitation: Wheel
# Do some other visitation: Wheel
# Do some other visitation: Wheel
# Do some other visitation: Wheel
# Do some other visitation: Body
# Do some other visitation: Engine
# Do some other visitation: Car