regex - (rails) validating URL help with regexp -

I'm using the following to verify if a URL is formatted correctly: / P>

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

However, when the URL does not start with http: // or does not work or https: // . Are there some similar ways to validate the URL with URI :: regexp (or URI ) and it is to include a valid URL which is http: // ? (For example, www.google.com is valid, as is http://www.google.com )

provides a strong regex:

  \ b (([\ w-] +: //? | Www [.]] [^ \ S () ] + (?: \ ([\ W \ d] + \) | ([^ [: punct:] \ s] | /)) ) Improvement in (NB Newline and Indentation has been added here for clarity, see the post for a more expanded version with explanation):  
 < Code> (? I) \ b ((?: [As] [\ w -] +: (?: / {1,3} | [a-z0- 9%]) | www \ d {0,3} [.] | [A-z0-9]. [-] [[.] [Ed] {2,4} /) (?: [^ \ S ( ) <+ + | \ (([^ \ S ())  | + | (\ [[^ \ s ()] ] + \)) * \)) + (?: \ (([^ \ S ())  | + | (\ [[^ \ s ()] ] + \)) * * *] = [^ \ S`! () \ [\] {} :: '., <<>  URL :: regexp  is a URI in its definition of loose (although it requires http ...). 
 
 You can use a virtual attribute or filter to add  before_save  to a  http: //  if necessary On url