Customise authenticate_user devise - ruby-on-rails

Question

Currently I have an Ajax call via a button click that updates a shopping cart, but the controller that it posts to has the authenticate_user! before_filter applied, which is what I want, as a user must be logged in.
Because it's an ajax call I normally just get a 401 error and no redirect, so to solve this I have:
$(document).on "ajaxError", (event, request, settings) ->
if request.status == 401
window.location.href = '/users/login'
However this is causing me issues with getting the flash[:notice] to appear as it's lost by the time i get to the login page.
From doing some reading on various posts on here I understand that I can use flash.keep which would persist my message, but I think to do that I am going to have to change my approach on handling the redirect. If I can do this in the controller I could also use if request.xhr?, couldn't I?
My question is how would I add this functionality whilst keeping all existing functionality of the authenticated_user! helper method. From looking at the devise docs the helper is dynamically built, isn't it?
I know I could put a helper into my application controller:
def authenticate_user!
super
end
So expanding on that I have tried
def authenticate_user!
if request.xhr?
respond_to do |format|
format.html { redirect_to new_user_session_path }
end
else
super
end
But when clicking the update button, which is this
$(window).load ->
$('a[data-target]').click (e) ->
e.preventDefault()
$this = $(this)
if $this.data('target') == 'Add to'
url = $this.data('addurl')
new_target = "Remove from"
else
url = $this.data('removeurl')
new_target = "Add to"
$.ajax url: url, type: 'put', success: (data) ->
$('.badge-number').html(data)
$this.find('span').html(new_target)
$this.data('target', new_target)
I get this error in the console
Routing Error
No route matches [PUT] "/users/login"
Not sure where to go from here.

Answer 1

This sounds quite high-friction from the user point of view. If I click "add to cart", I expect the thing to be added to the cart. I certainly don't expect to be redirected to a login/signup page. At this point, I would just navigate away.
A better approach is, if user is not logged in, create a guest user and write its id to the cookies. Guest user has cart, can add stuff, etc.
Then, at checkout page, you offer the choice "login" / "sign up". In either case, you get a real user. At which point you migrate guest cart and delete the guest user.
Example:
def current_or_guest_user
return guest_user unless current_user
# current user exists. And we found a guest user
if session[:guest_user_id]
transfer_guest_user_stuff # cart, posts and what-have-you
guest_user.destroy
session[:guest_user_id] = nil
end
current_user
end
def guest_user
unless #cached_guest_user
#cached_guest_user = User.find_or_create_by(id: session[:guest_user_id], is_guest: true)
session[:guest_user_id] = #cached_guest_user.id
end
#cached_guest_user
end

Answer 2

As the first piece of advice, You could use Trubolinks gem which provide all AJAX functionality "in-box" and is default in Rails 4+.
As the second piece of advice, You could generate Users Controler ( rails generate devise:controllers Users) and\or Devise modules such as sessions. passwords and other controlers with Customize Devise Tools.
Additionally, You could customize before_filter in certain Controller's code, for example:
class TicketsController < ApplicationController
before_filter :store_location
before_filter :authenticate_user!, :only => [:new, :delete]
In this sample, :authenticate_user should be only for :new and :delete methods. Other methods not require users authentication ...
I hope it help You!