Singleton

The Singleton module implements the Singleton pattern.

Installation

Add this line to your application's Gemfile:

gem'singleton'

And then execute:

$ bundle

Or install it yourself as:

$ gem install singleton

Usage

To use Singleton, include the module in your class.

classKlassincludeSingleton# ...end

This ensures that only one instance of Klass can be created.

a,b=Klass.instance,Klass.instancea == b# => trueKlass.new# => NoMethodError - new is private ...

The instance is created at upon the first call of Klass.instance().

classOtherKlassincludeSingleton# ...endObjectSpace.each_object(OtherKlass){}# => 0OtherKlass.instanceObjectSpace.each_object(OtherKlass){}# => 1

This behavior is preserved under inheritance and cloning.

Development

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. 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/ruby/singleton.