Description

This library provides Java style interfaces for Ruby.

Installation

gem install interface

Adding the trusted cert

gem cert --add <(curl -Ls https://raw.githubusercontent.com/djberg96/interface/main/certs/djberg96_pub.pem)

Synopsis

require 'interface'

MyInterface = interface do
  required_methods :foo, :bar, :baz
end

# Raises an error until 'baz' is defined
class MyClass
  implements MyInterface

  def foo
    puts "foo"
  end

  def bar
    puts "bar"
  end

  # Uncomment to work
  # def baz; end
end

General Notes

Sub-interfaces work as well. See the example_sub.rb file under the 'examples' directory for a sample sub-interface.

Developer's Notes

A discussion on IRC with Mauricio Fernandez got us talking about traits. During that discussion I remembered a blog entry by David Naseby. I revisited his blog entry and took a closer look:

http://ruby-naseby.blogspot.com/2008/11/traits-in-ruby.html

Keep in mind that I also happened to be thinking about Java at the moment because of a recent job switch that involved coding in Java. I was also trying to figure out what the purpose of interfaces were.

As I read the first page of David Naseby's article I realized that, whether intended or not, he had implemented a rudimentary form of interfaces for Ruby. When I discovered this, I talked about it some more with Mauricio and he and I (mostly him) fleshed out the rest of the module, including some syntax improvements. The result is syntax and functionality that is nearly identical to Java.

I should note that, although I am listed as the author, this was mostly the combined work of David Naseby and Mauricio Fernandez. I just happened to be the guy that put it all together.

In more recent versions this code was enhanced with the help of AI. Specifically, it was updated to use the TracePoint class so that an interface could be declared at the top of the class, with the method validations deferred.

Acknowledgements

This module was largely inspired and somewhat copied from a post by David Naseby (see URL above). It was subsequently modified almost entirely by Mauricio Fernandez through a series of discussions on IRC, and later by evil AI bots that will eventually kill us all.

See Also

The Crystal programming language, which has syntax very similar to Ruby's, effectively implements interfaces via the abstract keyword.

Copyright

(C) 2004-2025 Daniel J. Berger All rights reserved.

Warranty

This package is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose.

License

Artistic-2.0

Author

Daniel J. Berger