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GitHub User: sirfilip
Well i started as a RoR developer now active PHP developer (but with rails 3 i definitely consider returning) i use hidden fields to accomplish this task. Since you are submitting the values going back and forward the model object is being populated with the previous values with one difference you always have to have all of the fields hidden (showing only the once that are getting populated by the step). Sorry for this late response but i hope it helps.
Anyway thanks a lot for screencasting about rails, if it wasn't for railscasts i dont think that rails would get this popularity which definitely deserves.