ruby on rails - Exception while uploading file -

i upgraded rails 3.2 rails 4. uploadind file in form cause

typeerror (wrong argument type actiondispatch::http::uploadedfile (expected string)) 

but commented lines in controller , still error! error appears in post request. trace: https://gist.github.com/mystdeim/6049670

cancan not yet offer rails 4 compatibility, sorry.

there few open issues rails 4, eg.

• cancan activemodel::forbiddenattributeserror rails 4
• scoped has been removed in rails 4 master

furthermore, ryan bates taking break summer. there other committers, activity very light. don't recommend using cancan in rails 4 project yet.