ios - 让 url = URL(字符串 : item)! 在 swift 中返回 nil

Question

真的搞不懂这个，URL 打印出来并且不等于 nil，当我粘贴它时它在浏览器中工作。有什么想法吗？

import UIKit

class WebViewController: UIViewController {

    var postLink: String = String()
    @IBOutlet weak var mywebView: UIWebView!

    override func viewDidLoad() {
        super.viewDidLoad()
        print(postLink)

        let attempt = postLink
        let url: URL = URL(string: attempt)!
        let request: URLRequest = URLRequest(url: url)
        mywebView.loadRequest(request)

    }

错误发生在:

let url: URL = URL(string: attempt)!

Answer 1

我猜你是从另一个 Controller 传递 urlString，而不是这样做

var postUrlString:String? //<-- make it optional 

override func viewDidLoad() {
   super.viewDidLoad()

   guard let urlString = postUrlString, // forced unwrapped 
         let url = URL(string: urlString)
        else {  return }  // if there is any optional we return 
 // else continue
        let request: URLRequest = URLRequest(url: url)
        mywebView.loadRequest(request)

}