undef - Why would you want to undefine a method in ruby?

Question

I\'ve never seen undef - or any thing else that allows you to undefine a method - in any other programming languages. Why is it needed in Ruby?

EDIT: I\'m not arguin

Answer 1

If your using Single Table Inheritance with an ORM, such as ActiveRecord, you may want to undefine the methods for fields which are not being used for a particular class/object.

# table: shapes, with columns: name, sides, radius, type
class Shape < ActiveRecord::Base
end

class Circle < Shape
end

class Square < Shape
  undefine_method :radius
end

Note: This doesn't actually work in ActiveRecord as it internally expects a method for every field to always be defined.

Note: A square does have a radius its just not commonly used, but you get the gist? Think of some property your storing in the database which a Circle has, but a Square does not.