Programming Ruby 3.3

Inheritance and Visibility

Method definition and class inheritance have a wrinkle, but it’s fairly obscure. Within a class definition, you can change the visibility of a method in an ancestor class. For example, you can do something like this:

class Base
  def a_method
    puts "Got here"
  end
  private :a_method
end

class MakeItPublic < Base
  public :a_method
end

class KeepItPrivate < Base
end

In this example, you could invoke a_method in instances of class MakeItPublic, but not via instances of Base or KeepItPrivate.

So, how does Ruby pull off this feat of having one method with two different visibilities? Simply put, it cheats.

If a subclass changes the visibility of a method in a parent, Ruby effectively ...