Swift 2：AnyObject？不可转换为 NSString

Question

我正在尝试使用会话检查现有登录，但出现此错误

'AnyObject?' is not convertible to 'NSString'; did you mean to use 'as!' to force downcast?

在这行代码

self.usernameLabel.text = prefs.valueForKey("USERNAME") as NSString

完整的代码块是这个

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var usernameLabel: UILabel!

//Check for existing login, else show login
override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(true)

    let prefs: NSUserDefaults = NSUserDefaults.standardUserDefaults()
    let isLoggedIn:Int = prefs.integerForKey("ISLOGGEDIN") as Int
    if (isLoggedIn != 1) {
        self.performSegueWithIdentifier("goToLogin", sender: self)
    } else {
        self.usernameLabel.text = prefs.valueForKey("USERNAME") as NSString
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


}

修复它的最佳方法是什么？

Answer 1

试试这个……

  if let username = prefs.valueForKey("USERNAME") as? String{
      self.usernameLabel.text = username
  }

或者如果你想使用 NSString ..（只是一个选项）

 if let username = prefs.valueForKey("USERNAME") as? NSString{
      self.usernameLabel.text = username
  }

Answer 2

将 NSString 更改为字符串，

self.usernameLabel.text = prefs.valueForKey("USERNAME") as? String

它运行良好，希望对您有所帮助

Swift 2：AnyObject？不可转换为 NSString

Swift 2: AnyObject? is not convertible to NSString

ios

alamofire

xcode7

swift2