How to implement thread comment in Rails?

I want to develop a thread comment list like this: http://www.reddit.com/r/IAmA/comments/gbmg3/ama_request_a_jersey_shore_cameraman/

Is there any op开发者_Python百科ensource gem for it ?

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It is quite simple. I prefer to use nested_sets. Check out this awesome_nested_set GEM. Some folks like acts_as_tree GEM. But nested_sets fits better your problem.