On Jul 8, 3:31 pm, diego scataglini <dwebsub... / gmail.com> wrote: > I believe that changes to a class don't modify its already existing > instances. But you can always add and remove behavior of an object. C:\>irb irb(main):001:0> class Foo; def sq(x) x*x end; end irb(main):002:0> f = Foo.new irb(main):003:0> f.sq( 12 ) => 144 irb(main):004:0> class Foo; def double(x) x+x end; end irb(main):005:0> f.double( 21 ) => 42 irb(main):006:0> class Foo; def sq(x) x*x*x end; end irb(main):007:0> f.sq( 12 ) => 1728