Samnang Chhun wrote in post #972157:
> I would like to know is there any ways to check is singleton class of an
> object already created?
>
> ex: obj.singleton_class_defined?

As an indirect test, you can't Marshal any object with a singleton class 
(although there are other kinds of object that you can't Marshal either)

irb(main):001:0> foo = "abc"
=> "abc"
irb(main):002:0> (Marshal.dump(foo) && false) rescue true
=> false
irb(main):003:0> def foo.zzz; end
=> nil
irb(main):004:0> (Marshal.dump(foo) && false) rescue true
=> true

-- 
Posted via http://www.ruby-forum.com/.