Validating UK postcodes with ActiveRecord validations

Validating UK postcodes with ActiveRecord is pretty straightforward. I grabbed a regular expression from this blog post and made it slightly more forgiving to accept postcodes without spaces (so that it accepts both SW1 1AB and SW11AB).

Here is a version with the regular expression inline:

And here is the custom validator version:

To use the custom validator bung the file in app/validators/ and use like so: