warden_strategies.rb

module Devise
  module Strategies
    class Token < Base

      # For more info. visit here..
      # http://kyan.com/blog/2013/10/11/devise-authentication-strategies
      def valid?
        token
      end

      # For this example, we are simply using token authentication
      # via parameters. However, anyone could use Rails's token
      # authentication features to get the token from a header.
      def authenticate!
        user = User.find_by_device_and_token(request.headers['X_MOBILE_DEVICE'], token)

        if user.present?
          User.current = user
          success!(user)
        else
          fail!("Could not log in")
        end
      end

      def token
        return params['auth_token'] if params['auth_token']
        header = request.headers["Authorization"]
        return unless header
        header.split("Token token=")[1]
      end

    end
  end
end