undef_method(...) public

Prevents the current class from responding to calls to the named method. Contrast this with remove_method, which deletes the method from the particular class; Ruby will still search superclasses and mixed-in modules for a possible receiver. 

   class Parent
     def hello
       puts "In parent"
     end
   end
   class Child < Parent
     def hello
       puts "In child"
     end
   end

   c = Child.new
   c.hello

   class Child
     remove_method :hello  # remove from child, still in parent
   end
   c.hello

   class Child
     undef_method :hello   # prevent any calls to 'hello'
   end
   c.hello

produces: 

   In child
   In parent
   prog.rb:23: undefined method `hello' for #<Child:0x401b3bb4> (NoMethodError)
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