How to check validity of URL in Swift?

Question

Trying to make an app launch the default browser to a URL, but only if the URL entered is valid, otherwise it displays a message saying the URL is invalid.

How would

Answer 1

This isn't a regex approach, but it is a naive one that works well for making sure there is a host and an extension if you want a simple and inexpensive approach:

extension String {
    var isValidUrlNaive: Bool {
        var domain = self
        guard domain.count > 2 else {return false}
        guard domain.trim().split(" ").count == 1 else {return false}
        if self.containsString("?") {
            var parts = self.splitWithMax("?", maxSplit: 1)
            domain = parts[0]
        }
        return domain.split(".").count > 1
    }
}

Use this only if you want a quick way to check on the client side and you have server logic that will do a more rigorous check before saving the data.

Answer 2

In some cases it can be enough to check that the url satisfies RFC 1808. There are several ways to do this. One example:

if let url = URL(string: urlString), url.host != nil {
  // This is a correct url
}

This is because .host, as well as .path, .fragment and a few other methods would return nil if url doesn't conform to RFC 1808.

If you don't check, you might have this kind of messages in console log:

Task <DF46917D-1A04-4E76-B54E-876423224DF7>.<72> finished with error - code: -1002

Answer 3

Swift 4.2 Elegant URL construction with verification

import Foundation
import UIKit

extension URL {

  init?(withCheck string: String?) {
    let regEx = "((https|http)://)((\\w|-)+)(([.]|[/])((\\w|-)+))+"
    guard
        let urlString = string,
        let url = URL(string: urlString),
        NSPredicate(format: "SELF MATCHES %@", argumentArray: [regEx]).evaluate(with: urlString),
        UIApplication.shared.canOpenURL(url)
        else {
            return nil
    }

    self = url
  }
}

Usage

var imageUrl: URL? {
    if let url = URL(withCheck: imageString) {
        return url
    }
    if let url = URL(withCheck: image2String) {
        return url
    }
    return nil
}

Answer 4

For Swift 4 version

static func isValidUrl (urlString: String?) -> Bool {
    if let urlString = urlString {
        if let url = URL(string: urlString) {
            return UIApplication.shared.canOpenURL(url)
        }
    }
    return false
}

Answer 5

extension String {    
    func isStringLink() -> Bool {
        let types: NSTextCheckingResult.CheckingType = [.link]
        let detector = try? NSDataDetector(types: types.rawValue)
        guard (detector != nil && self.characters.count > 0) else { return false }
        if detector!.numberOfMatches(in: self, options: NSRegularExpression.MatchingOptions(rawValue: 0), range: NSMakeRange(0, self.characters.count)) > 0 {
            return true
        }
        return false
    }
}

//Usage
let testURL: String = "http://www.google.com"
if testURL.isStringLink() {
    //Valid!
} else {
    //Not valid.
}

It's advised to use this check only once and then reuse.

_{P.S. Credits to Shachar for this function.}

Answer 6

var url:NSURL = NSURL(string: "tel://000000000000")!
if UIApplication.sharedApplication().canOpenURL(url) {
    UIApplication.sharedApplication().openURL(url)
} else {
     // Put your error handler code...
}