limiting access to a beta site

I'm just learning Rails. I tried to implement the code snippets in the
link above but have not been successful.

Would anyone be willing to test it and discuss? Do you have any other
approaches that work well for you? I'm also considering single- or
triple-use passwords/links in lieu of the login-password approach.

I listed some of the problems I had as comments on the linked page, and
I can provide more details. I'll add that I created a column in the
database for 'key' and created a field for it in the form, assuming that
the key is submitted with the form instead of being sent as a parameter
in a link (as the beta_key.rb implies).

Tom Calloway