remove_method.rb

class SomeClass
  def sumpm
    puts "You found me!"
  end

  def singleton_class
    class << self; self; end
  end

  def remove_method(method_name)
    copy = self.dup
    p copy.methods.sort
    p copy.singleton_class.instance_methods.sort
    copy.singleton_class.send(:undef_method,method_name)
    copy
  end

end

e = SomeClass.new
def e.blah
  puts "In blah"
end
e.blah
# This fails with method not found
x = e.remove_method(:blah)
x.blah
e.blah

# This works
e.sumpm
x = e.remove_method(:sumpm)
x.sumpm
e.sumpm