Form validation on non-CRUD activities

Hi there,

I'm relativity new to Rails (I've been eying it for some time, though). I'm reasonably familiar with Ruby's syntax.

When I pick up a new language, I like to make a simple blog. I'm focusing on the authentication at the moment. I am well aware of the existing plugins out there, but since this application will never see the light of day and I learning by rolling my own.

Now, let's say I have a login form, how do I validate that? I'm not saving into a model, or anything like that. At this stage, I'm just using a form_tag, and doing simple if params[:username] == '' in the controller. Very ugly indeed.

What is the best way to validate a form (and get the nice error messages, like when you are scaffolding) when you are not necessarily saving data?

Cheers. Tom.

Here's what i use -