- (BOOL) validateUrl: (NSString *) candidate {
    NSString *urlRegEx =
    @"(http|https)://((\w)*|([0-9]*)|([-|_])*)+([\.|/]((\w)*|([0-9]*)|([-|_])*))+";
    NSPredicate *urlTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", urlRegEx];
    return [urlTest evaluateWithObject:candidate];
}

let link =  "http://www.yourUrl.com".stringByRemovingPercentEncoding!.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)!

if let checkedUrl = NSURL(string: link) {
    // you can use checkedUrl here
}

func validateUrl (urlString: String?) -> Bool {
    let urlRegEx = "(http|https)://((\w)*|([0-9]*)|([-|_])*)+([\.|/]((\w)*|([0-9]*)|([-|_])*))+"
    return NSPredicate(format: "SELF MATCHES %@", urlRegEx).evaluateWithObject(urlString)
}

let regex = NSRegularExpression(pattern: "/^(https?://)?([da-z.-]+).([a-z.]{2,6})([/w .-]*)*/?$/",options: nil, error: nil)!

if regex.firstMatchInString(searchTerm!, options: nil, range: NSMakeRange(0, searchTerm!.length)) != nil {
    println("not valid url ")
}

func checkGivenUrl(userURL:String) -> Bool {

    let userURL:String =  userURL

    do {
        let checkReg = try NSRegularExpression(pattern: "(http|https)://([A-Z]|[a-z].)|([A-Z]|[a-z]|[0-9]+)*.([a-z]|[A-Z])", options: .CaseInsensitive)

        if checkReg.firstMatchInString(userURL, options: .ReportCompletion, range: NSMakeRange(0, userURL.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))) != nil {

            if let url = NSURL(string: userURL) {
            if UIApplication.sharedApplication().canOpenURL(url) {

                return true
            }
            }
            return false
        }

    }

    catch
    {
        print("Error")
    }


    return false
}

requestedURL = "http://google.com"
   if checkGivenUrl(requestedURL!) == true {
    performSegueWithIdentifier("gotoWebView", sender: self)
    }
    else{
        let alert = UIAlertController(title: "Failed", message: "Enter a valid URL", preferredStyle: .Alert)
        alert.addAction(UIAlertAction(title: "Dismiss", style: .Cancel, handler: nil))

        self.presentViewController(alert, animated: true, completion: nil)
    }
}

func validateUrl() -> Bool {
  let urlRegEx = "((\w)*|([0-9]*)|([-|_])*)+([\.|/]((\w)*|([0-9]*)|([-|_])*))+"
  return NSPredicate(format: "SELF MATCHES %@", urlRegEx).evaluate(with: self)
}

func fooBar(textField: UITextField) {
   if textField == someTextField {
      if textField.text?.validateUrl() == true {
         print("true")
      } else {
         print("false")
      }
   }
}

import Foundation
import UIKit

extension String {

    var canOpenURL : Bool {

        guard let url = NSURL(string: self) else {return false}
        if !UIApplication.shared.canOpenURL(url as URL) {return false}
        let regEx = "((https|http)://)((\w|-)+)(([.]|[/])((\w|-)+))+"
        let predicate = NSPredicate(format:"SELF MATCHES %@", argumentArray:[regEx])
        return predicate.evaluate(with: self)
    }
}

if textField == someTextField {

    if (self.textField.text?.canOpenURL)! {
        //URL valid
    }else {
       //URL invalid
    }
}

(https?://(www.)?)?[-a-zA-Z0-9@:%._+~#=]{2,256}.[a-z]{2,6}b([-a-zA-Z0-9@:%_+.~#?&//=]*)

func validateURL (urlString: String) -> Bool {
    let urlRegEx = "(https?://(www.)?)?[-a-zA-Z0-9@:%._+~#=]{2,256}.[a-z]{2,6}b([-a-zA-Z0-9@:%_+.~#?&//=]*)"
    let urlTest = NSPredicate(format:"SELF MATCHES %@", urlRegEx)
    return urlTest.evaluate(with: urlString)
}