(rails) validating URL help with regexp

Question

i'm using the following to verify if a URL is formatted validly:

validates_format_of :website, :with => URI::regexp(%w(http https))

however, it doesn't work when the url doesn't start with http:// or https://. Is there some similar way to validate URLs with URI::regexp (or URI) and make it include valid URLs that don't start with http://? (For example, www.google.com is valid, as is http://www.google.com)

Answer 1

This post on Daring Fireball provides a robust regex:

\b(([\w-]+://?|www[.])[^\s()<>]+(?:\([\w\d]+\)|([^[:punct:]\s]|/)))

A more recent post improves on it (N.B. newlines and indentation added here for clarity; see the post for an even more expanded version with explanations):

(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|
           www\d{0,3}[.]|
           [a-z0-9.\-]+[.][a-z]{2,4}/)
       (?:[^\s()<>]+|
          \(([^\s()<>]+|
          (\([^\s()<>]+\)))*\))+
       (?:\(([^\s()<>]+|
          (\([^\s()<>]+\)))*\)|
          [^\s`!()\[\]{};:'".,<>?«»“”‘’]))

From my tests URL::regexp is to loose in its definition of a URI (though it does require http…).

You can use a virtual attribute or before_save filter to append a http:// to your URLs if necessary.