Question

I need to check that the user is still logged in so that I can prevent them from even opening the form if their session expired (logged out but page hasn’t been refreshed).

Here’s the pseudo code of what I was trying to do, doesn’t work obviously.

// some view.html
$('#someform').click(function() {
    ajax(URL('login_status'), [], '');
});

// some controller.py
def login_status():
    if not auth.user:
        redirect('index')

Answer 1

If you want the full page to redirect as the result of an Ajax request, you’ll have to do it via Javascript on the client rather than via a server-side redirect (which will only redirect the Ajax request itself). To make that happen, you can specify “:eval” as the target in the ajax() function, which will result in the returned response being executed as Javascript code (see here). So, something like:

$('#someform').click(function() {
    ajax("{{=URL('default', 'login_status')}}", [], ':eval');
});

// some controller.py
def login_status():
    if auth.user:
        return 'this.show()' # or appropriate Javascript code to show the form
    else:
        return 'window.location = "%s"' % URL('default', 'index')

So, the Ajax call returns Javascript that either shows the form or redirects the page, depending on whether the user is logged in.

Also, note that the URL() function is a server-side Python function, so you can’t just call it within the ajax() function, which is a client-side Javascript function. Instead, you have to put it inside web2py’s template delimiters ({{ }}) so the URL will be generated in the template on the server.

UPDATE: Instead of:

return 'window.location = "%s"' % URL('default', 'index')

you can now do:

redirect(URL('default', 'index'), client_side=True)

which will do the same thing behind the scenes.