ruby on rails 3 - Validating Password using Regex

Question

I am working on a Rails 3 application that needs to validate the password based on the following criteria: must be at least 6 characters and include one number and one letter.

Here is my Regex:

validates :password, :format => {:with => /^[([a-z]|[A-Z])0-9_-]{6,40}$/, message: "must be at least 6 characters and include one number and one letter."}

Right now if I put in a password of (for ex: dogfood) it will pass. But what I need it to do is to pass the criteria above.

I am not all that great at regex, so any and all help is greatly appreciated!

Answer 1

Use lookahead assertions:

/^(?=.*[a-zA-Z])(?=.*[0-9]).{6,}$/
  |             |          |
  |             |          |
  |             |          Ensure there are at least 6 characters.
  |             |
  |             Look ahead for an arbitrary string followed by a number.
  |                        
  Look ahead for an arbitrary string followed by a letter.

Technically in this case you don't need the anchors, but it's good habit to use them.