Ajax live valiation on username

This has probably been definitively answered elsewhere (it applies to
the default setup for restful_authentication), but I haven't been able
to track the solution down. My User model has a unique 'username' (or
:login, as it's known in RA) attribute, and it's going to be very
annoying for users to have to wait until a form is posted to find out
that their chosen username is already taken. Does anyone know of an easy
route for doing client side validation on this attribute? I think it's
the only attribute I need to do the client side validation on, and I
just want it to confirm whether or not a username is available, on the
fly...

Any plugins, blog posts, quick tips?

I found this post but, knowing the pace of Rails and considering it was
posted almost two years ago, I'm betting there's something newer out
there, plus it doesn't come with any specs;

http://www.davidjrice.co.uk/articles/2006/11/29/inline-ajax-form-validation-plugin-for-ruby-on-rails

Neil Cauldwell wrote:

This has probably been definitively answered elsewhere (it applies to
the default setup for restful_authentication), but I haven't been able
to track the solution down. My User model has a unique 'username' (or
:login, as it's known in RA) attribute, and it's going to be very
annoying for users to have to wait until a form is posted to find out
that their chosen username is already taken. Does anyone know of an easy
route for doing client side validation on this attribute? I think it's
the only attribute I need to do the client side validation on, and I
just want it to confirm whether or not a username is available, on the
fly...

Any plugins, blog posts, quick tips?

I found this post but, knowing the pace of Rails and considering it was
posted almost two years ago, I'm betting there's something newer out
there, plus it doesn't come with any specs;

http://www.davidjrice.co.uk/articles/2006/11/29/inline-ajax-form-validation-plugin-for-ruby-on-rails

Update: These are probably the easiest tutorials to follow;

http://apidock.com/rails/ActionView/Helpers/PrototypeHelper/observe_field
http://weblogs.java.net/blog/bleonard/archive/2008/04/autovalidation.html

Just make sure you manage your :validate action in relation to any
before filters you may have in your users controller.