Prependers

Prependers are a way to easily and cleanly extend third-party code via Module#prepend.

Installation

Add this line to your application's Gemfile:

gem 'prependers'

And then execute:

$ bundle

Or install it yourself as:

$ gem install prependers

Usage

To define a prepender manually, simply include the Prependers::Prepender.new module. For instance, if you have installed an animals gem and you want to extend the Animals::Dog class, you can define a module like the following:

module Animals::Dog::AddBarking
  include Prependers::Prepender.new

  def bark
    puts 'Woof!'
  end
end

Animals::Dog.new.bark # => 'Woof!'

Extending class methods

If you want to extend a module's class methods, you can define a ClassMethods module in your prepender:

module Animals::Dog::AddFamily
  include Prependers::Prepender.new

  module ClassMethods
    def family
      puts 'Canids'
    end
  end
end

Animals::Dog.family # => 'Canids'

As you can see, the ClassMethods module has automagically been prepended to the Animals::Dog's singleton class.

Autoloading prependers

If you don't want to include Prependers::Prepender, you can also autoload prependers from a path, they will be loaded in alphabetical order.

Here's the previous example, but with autoloading:

# app/prependers/animals/dog/add_barking.rb
module Animals::Dog::AddBarking
  def bark
    puts 'Woof!'
  end
end

# somewhere in your initialization code
Prependers.load_paths(File.expand_path('app/prependers'))

You can pass multiple arguments to #load_paths, which is useful if you have subdirectories in app/prependers:

Prependers.load_paths(
  File.expand_path('app/prependers/controllers'),
  File.expand_path('app/prependers/models'),
  # ...
)

Note that, in order for autoprepending to work, the paths of your prependers must match the names of the prependers you defined.

Using a namespace

It can be useful to have a prefix namespace for your prependers. That way, you don't have to worry about accidentally overriding any vendor modules. This is actually the recommended way to define your prependers.

You can accomplish this by passing an argument when including the Prependers::Prepender module:

module MyApp
  module Animals
    module Dog
      module AddBarking
        include Prependers::Prepender.new(MyApp)

        def bark
          puts 'Woof!'
        end
      end
    end
  end
end

If you use autoloading, you can pass the base namespace to #load_paths:

Prependers.load_paths(File.expand_path('app/prependers'), namespace: MyApp)

Integrating with Rails

To use prependers in your Rails app, simply create them under app/prependers/models, app/prependers/controllers etc. and add the following to your config/application.rb:

Prependers.setup_for_rails

If you want to use a namespace, just pass the :namespace option to #setup_for_rails and name your files and modules accordingly.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec 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. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/nebulab/prependers.

License

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