Is the regular expression that calls the string "a? C" invalid?

Question

In my user model, I have the attribute "nickname" and is checked as such:

validates_format_of: nickname ,: with => / [a-zA-Z0-9] $ /,: allow_nil => true

However, this string is currently passed as valid:

a? WITH

I only want to accept alphanumeric strings - does anyone know why my regex doesn't work? If anyone can offer a better regex, I'm all ears.

Answer 1

You need to bind the template on both sides:

/^[a-zA-Z0-9]+$/ 

Answer 2

This will be true if the string ends with a valid character. No check for anything in the middle. Try the following:

 ^[a-zA-Z0-9]*$