Question

我使用this教程创建了一个应用。但这是行不通的。我写的一切都像在教程中一样。但是此代码不起作用。而且它不想转换为Swift 4。这是我的代码：

import UIKit
import LocalAuthentication

class ViewController: UIViewController {

func showAlertController(_ message: String) {
    let alertController = UIAlertController(title: nil, message: message, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
    present(alertController, animated: true, completion: nil)
}

@IBAction func touchID(_ sender: Any) {

    let context = LAContext()
    var error: NSError?



    if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
        let reason = "Authenticate with Touch ID"
        context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason, reply:
            {(succes, error) in
                if succes {
                    self.showAlertController("Touch ID Authentication Succeeded")
                }
                else {
                    self.showAlertController("Touch ID Authentication Failed")
                }
                } as! (Bool, Error?) -> Void)
    }

    else {
        showAlertController("Touch ID not available")
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

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

}

这是一个错误：

38:23 Expression type '(Bool, Error?) -> Void' is ambiguous without more context

和

38:23 Cast from '(_, _) -> ()' to unrelated type '(Bool, Error?) -> Void' always fails

Answer 1

表达类型'（Bool，Error？）-> Void'模棱两可，没有更多上下文，因为它总是失败，所以只需删除：

as! (Bool, Error?) -> Void

还有哪些额外的内容，如下所示：

if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
    let reason = "Authenticate with Touch ID"
    context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason, reply:
        {(succes, error) in
            if succes {
                self.showAlertController("Touch ID Authentication Succeeded")
            }
            else {
                self.showAlertController("Touch ID Authentication Failed")
            }
            } )
}
else {
    showAlertController("Touch ID not available")
}

表达式类型'（Bool，Error？）-> Void'不明确，没有更多上下文

1 个答案: