Alternatives

There are several other libraries out there that implement interfaces in various ways:

• https://github.com/kklimuk/ruby_interface
• https://github.com/shuber/interface
• https://github.com/andrzejsliwa/oop-interface

However, one advantage that my library has over these is that it checks the moment the interface is included, rather than deferring the check until you try to instantiate it or explicitly check for its validity.