Rails custom validation based on a regex?

Question

I have the following regex that I use in my routes.rb for /type-in-something-here

# A-Z, a-z, 0-9, _ in the middle but never starting or ending in a _
# At l         


        

Answer 1

For validation purposes, remember to add the beginning and end of string markers \A and \Z:

validates_format_of :uuid, :with => /\A[A-Za-z\d]([-\w]{,498}[A-Za-z\d])?\Z/i

Otherwise your regex will happily match any string that contains at least a letter or a digit. For some reason Rails implicitly adds the boundaries in the routes. (Probably because it embeds the regex inside a larger one to match the entire URL, with explicit checks for / and the end of the URL.)