Ruby & Rails Ruby

Ruby specific OOP concepts

https://launchschool.com/books/oo_ruby/read/the_object_model (Novice)
https://launchschool.com/books/oo_ruby/read/classes_and_objects_part1 (Novice)
https://launchschool.com/books/oo_ruby/read/classes_and_objects_part2 (Novice)
https://launchschool.com/books/oo_ruby/read/inheritance (Novice)
https://medium.com/launch-school/the-basics-of-oop-ruby-26eaa97d2e98 (Advanced)
https://medium.com/rubycademy/understanding-the-eigenclass-in-less-than-5-minutes-dcb8ca223eb4 (Advanced)
https://pawelurbanek.com/ruby-abstract-class (Advanced)
http://patshaughnessy.net/ruby-under-a-microscope (Advanced)