login session controller for devise receiver from mobile (phonegap) client

gistfile1.rb

class Api::SessionsController < Devise::SessionsController
  # include Devise::Controllers::InternalHelpers
  prepend_before_filter :require_no_authentication, :only => [:new, :create]

  def new
    super
  end

  def create
    sign_out(current_user) if current_user
    @user = warden.authenticate(:scope => :user)
    if @user && @user.valid_password?(params[:user][:password])
      sign_in(@user)
      @user.reset_authentication_token!
      render :json => {
        :access_token => @user.authentication_token, 
        :token_type => "persistant", 
        :user_id => @user.id, 
        :user => @user.as_json(root: false),
        :studies => @user.studies.as_json(root: false)
      }, :callback => params[:callback]
    else
      render :json => {:error => "Invalid Login Credentials"}, :callback => params[:callback]
    end
  end

end