Question

I need to validate url, so I used site http://www.rubular.com/ and maybe I get wrong result. So I wrote this: w{3}\.[a-z]+\.[a-z]{3} in http://www.rubular.com/ and it gived me almost wanted result. In my model Website I wrote:

 VALID_URL_REGEX = /w{3}\.[a-z]+\.[a-z]{3}/
 validates :url, :presence => true, format: { with: VALID_URL_REGEX }

Question : how I can make to check, that last part should contain only 3 letters ?

Answer 1

You have to use \A and \z to match against start and end of string.

Like this: /\Aw{3}\.[a-z]+\.[a-z]{3}\z/.

But like Mahmoud Al-Qudsi said, tlds can have more or less than 3 letters.
And you should make it match multiple subdomains or naked domains (e.g. stackoverflow.com instead of http://www.stackoverflow.com).

I came up with this /\A(?:[\w-]+(?<!-)\.){1,}[\w]{2,}\z/.