Rails: undefined method `model_name'?

Getting a strange error when trying to output some data as a response to a j开发者_Go百科son request. For the life of me I cannot figure out the problem here. I am doing something very similar in another controller and not getting any error at all. Any ideas what would be causing this?

  class SessionsController
  ...
  user = User.authenticate(params[:session][:email].downcase,
                           params[:session][:password].downcase)
  if user.nil?
    respond_with(@error = "Invalid email/password combination.")
  else
    sign_in user
    respond_with([user, user.authenticated_with])
  end

  -------------------------------------

  User.rb
  ...
  def authenticated_with
    fb_hash = {:facebook => (!self.authentications.where("provider = ?", "facebook").empty? ? true : false)}
    tw_hash = {:twitter => (!self.authentications.where("provider = ?", "twitter").empty? ? true : false)}
    providers = [fb_hash, tw_hash]
    return providers
  end

  -------------------------------------

  LOG OUTPUT

  2011-09-05T15:25:51+00:00 app[web.1]: NoMethodError (undefined method `model_name' for Array:Class):
  2011-09-05T15:25:51+00:00 app[web.1]:   app/controllers/sessions_controller.rb:24:in `create'

The log error is referencing this line:

  respond_with([user, user.authenticated_with])

Any ideas???

Thanks!

My solution for anyone who finds this. I ended up rewriting

respond_with()

as a respond_to block:

respond_to do |format|
  format.json { render :json => [user, user.authenticated_with]}
end

This solved the problem for me!