VCard Upload Import

I’m trying to add Vcard import functionality and I keep getting the
following using the code provided below. I’m using the VPIM library
to decode the vcards and add them to my database table. Can someone
help me out, or point me in a different direction for importing
VCards. Thanks.

Error:
cannot convert StringIO into String

Controller Code:
require ‘vpim/vcard’

if request.post? and params[:import_file]
cards = Vpim::Vcard.decode(File.open(params[:import_file]))
end