OpenHouse

OpenHouse provides a module which simplifies implementing the Visitor design pattern on a type hierarchy.

Add this line to your application's Gemfile:

gem 'openhouse'

And then execute:

$ bundle

Or install it yourself as:

$ gem install openhouse

Here is a simple example:

class EmperorPenguin

  include OpenHouse::Acceptor

  attr_reader :weight

  def initialize(weight)
    @weight = weight
  end

end

class AnimalAnnouncerVisitor

  def visit_emperor_penguin(emperor_penguin)
    "This is an emperor penguin that weights #{emperor_penguin.weight} kg."
  end

end

animal  = EmperorPenguin.new(42)
visitor = AnimalAnnouncerVisitor.new

animal.accept_visitor(visitor)

An example with a full type hierarchy that shows more features can be found in the test files.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

Bug reports and pull requests are welcome on GitHub at https://github.com/eugeniobruno/openhouse. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.