swift - URL 验证无法快速工作

Question

两周前开始学习 swift，之前没有任何编程经验，我终究无法弄清楚为什么检查 nil 不起作用。如果用户输入无效的 URL，它只会在尝试加载网页时崩溃。这是完整的代码。

import UIKit; import WebKit

class ViewController: UIViewController {

@IBOutlet weak var adressBar: UITextField!
@IBOutlet weak var webView: WKWebView!

override func viewDidLoad() {
    super.viewDidLoad()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

@IBAction func returnPressed(_ sender: Any) {
    if let adressBarText = adressBar.text {
        if let myURL = URL(string: adressBarText) {
            let myRequest = URLRequest(url: myURL)
            webView.load(myRequest)

            adressBar.resignFirstResponder()
            print("EYYYYY")
        } else {
            print("BOOOO")
        }
    }
}

Answer 1

试试这个方法

func verifyUrl (urlString: String?) -> Bool {
    //Check for nil 
    if let urlString = urlString { 
        // create NSURL instance
        if let url = NSURL(string: urlString) {
            // check if your application can open the NSURL instance 
            return UIApplication.sharedApplication().canOpenURL(url)
        }
    }

    return false
}

https://stackoverflow.com/a/30130535/8069241