The Well-Grounded Rubyist, Second Edition

3.5. Inheritance and the Ruby class hierarchy

Inheritance is a kind of downward-chaining relationship between two classes (the superclass and the subclass), whereby one class “inherits” from another and the instances of the subclass acquire the behaviors—the methods—defined in the superclass.

In this example, Magazine inherits from Publication. Note the syntax in Magazine’s class definition:

class Publication
  attr_accessor :publisher
end

class Magazine < Publication
  attr_accessor :editor
end

The symbol < designates Magazine as a subclass of Publication. Because every publication object has publisher and publisher= methods (thanks to attr_accessor :publisher), every magazine object has those methods too. In addition, magazine objects have editor ...