How can you check to see if a URL is valid in Swift 4? I'm building a simple web browser for personal use and even though I know to enter the full URL each time I'd rather get an alert instead of the app crashing if I forget.
import UIKit
import SafariServices
class MainViewController: UIViewController {
@IBOutlet weak var urlTextField: UITextField!
@IBAction func startBrowser(_ sender: Any) {
if let url = self.urlTextField.text {
let sfViewController = SFSafariViewController(url: NSURL(string: url)! as URL)
self.present(sfViewController, animated: true, completion: nil)
}
print ("Now browsing in SFSafariViewController")
}
}
For example, if I was to type in a web address without http:// or https:// the app would crash with the error 'NSInvalidArgumentException', reason: 'The specified URL has an unsupported scheme. Only HTTP and HTTPS URLs are supported.'
You're probably crashing because you're using the !
operator and not checking that it will work. Instead try:
@IBAction func startBrowser(_ sender: Any) {
if let urlString = self.urlTextField.text {
let url: URL?
if urlString.hasPrefix("http://") {
url = URL(string: urlString)
} else {
url = URL(string: "http://" + urlString)
}
if let url = url {
let sfViewController = SFSafariViewController(url: url)
self.present(sfViewController, animated: true, completion: nil)
print ("Now browsing in SFSafariViewController")
}
}
}
This should give you the idea of how to handle the different cases, but you probably want something more sophisticated which can deal with https and strips whitespace.