title: Ruby execute self.included(base) method on sub classes without explicit include declaration?
body: <p>I have a number of classes that inherit from one superclass.
  The superclass as a module defined. Inside of a module is a self.included(base) method that sets some instance variables.</p>
  
  <p>So something like this:</p>
  
  <pre><code>module MyModule
    def self.included(base)
      base.instance_variable_set("@my_instance_variable", {})
    end
  end
  
  class MySuperClass
    include MyModule
  end
  
  class ClassA &lt; MySuperClass
  end
  
  class ClassB &lt; MySuperClass
  end
  </code></pre>
  
  <p>Unless I explicitly include MyModule in ClassA and ClassB then my instance variable will not get set in these two classes.</p>
  
  <p>Is there a way of making sure the modules self.included(base) method is executed in each sub class without the need to explicitly include the module? Since it's already included in the superclass.</p>