使用 swiftUI 进行生物特征认证评估 [英] Biometric Authentication evaluation with swiftUI

问题描述

我已经能够在我的应用程序中使用基本版本的 Face/Touch ID.但是，我想添加更好的回退和错误处理.

I've been able to get a rudimentary version of Face / Touch ID working inside my app. However, I want to add better fallbacks and error handling.

所以我一直在研究如何去做.有很多这样的资源:

So I've been researching how to do it. There are fantastic resources like this:

面容 ID 评估过程无法正常工作

但是，我在 SwiftUI 视图中找不到任何可用的东西.目前我的项目不会运行:

However, I can't find anything that works inside a SwiftUI view. At the moment my project won't run with:

'unowned' may only be applied to class and class-bound protocol types, not 'AuthenticateView'

和

Value of type 'AuthenticateView' has no member 'present'

任何帮助将不胜感激.谢谢！

any help would be much appreciated. Thank you!

这是我在 AuthenticateView.swift 中的代码

Here's my code inside AuthenticateView.swift

func Authenticate(completion: @escaping ((Bool) -> ())){

    //Create a context
    let authenticationContext = LAContext()
    var error:NSError?

    //Check if device have Biometric sensor
    let isValidSensor : Bool = authenticationContext.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error)

    if isValidSensor {
        //Device have BiometricSensor
        //It Supports TouchID

        authenticationContext.evaluatePolicy(
            .deviceOwnerAuthenticationWithBiometrics,
            localizedReason: "Touch / Face ID authentication",
            reply: { [unowned self] (success, error) -> Void in

                if(success) {
                    // Touch / Face ID recognized success here
                    completion(true)
                } else {
                    //If not recognized then
                    if let error = error {
                        let strMessage = self.errorMessage(errorCode: error._code)
                        if strMessage != ""{
                            self.showAlertWithTitle(title: "Error", message: strMessage)
                        }
                    }
                    completion(false)
                }
        })
    } else {

        let strMessage = self.errorMessage(errorCode: (error?._code)!)
        if strMessage != ""{
            self.showAlertWithTitle(title: "Error", message: strMessage)
        }
    }
}

func errorMessage(errorCode:Int) -> String{

    var strMessage = ""

    switch errorCode {

    case LAError.Code.authenticationFailed.rawValue:
        strMessage = "Authentication Failed"

    case LAError.Code.userCancel.rawValue:
        strMessage = "User Cancel"

    case LAError.Code.systemCancel.rawValue:
        strMessage = "System Cancel"

    case LAError.Code.passcodeNotSet.rawValue:
        strMessage = "Please goto the Settings & Turn On Passcode"

    case LAError.Code.touchIDNotAvailable.rawValue:
        strMessage = "TouchI or FaceID DNot Available"

    case LAError.Code.touchIDNotEnrolled.rawValue:
        strMessage = "TouchID or FaceID Not Enrolled"

    case LAError.Code.touchIDLockout.rawValue:
        strMessage = "TouchID or FaceID Lockout Please goto the Settings & Turn On Passcode"

    case LAError.Code.appCancel.rawValue:
        strMessage = "App Cancel"

    case LAError.Code.invalidContext.rawValue:
        strMessage = "Invalid Context"

    default:
        strMessage = ""

    }
    return strMessage
}

func showAlertWithTitle( title:String, message:String ) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)

    let actionOk = UIAlertAction(title: "OK", style: .default, handler: nil)
    alert.addAction(actionOk)
    self.present(alert, animated: true, completion: nil)
}

推荐答案

说明:

'unowned' 只能应用于类和类绑定的协议类型，而不是 'AuthenticateView'

'unowned' may only be applied to class and class-bound protocol types, not 'AuthenticateView'

首先，你有 AuthenticateView，它是一个 struct.你不能这样做 class 因为整个 Apple 的 SwiftUI 想法 都是关于结构的. 因为 Struct 是值类型而不是引用类型，所以没有指针.因此，您不能将包含 unowned self 和 weak self 修饰符的代码部分包含到 struct AuthenticateView: View {}

First of all, you have AuthenticateView which is a struct. You can't do it class because whole Apple's SwiftUI idea is about structures. And because Struct is value type and not a Reference type, so no pointer as such. So you may not include code parts containing unowned self and weak self modifiers into struct AuthenticateView: View {}

'AuthenticateView' 类型的值没有成员 'present'

Value of type 'AuthenticateView' has no member 'present'

present 是一个 UIViewController 的方法.在 SwiftUI 中，您无法访问它.使用下一种样式显示警报:

present is a UIViewController's method. Here in SwiftUI you have no access to it. The alerts are being presented using the next style:

struct ContentView: View {
    @State private var show = false
    var body: some View {
        Button(action: { self.show = true }) { Text("Click") }
        .alert(isPresented: $showingAlert) {
            Alert(title: Text("Title"), 
                message: Text("Message"), 
          dismissButton: .default(Text("Close")))
        }
    }
}

解决办法:对于您的情况，我将为您的逻辑创建 ObservableObject 的 class Handler 子类，并使用 @ObservedObject、@Published 和 @State.

Solution: For your case, I would create a class Handler subclass of ObservableObject for your logic and use the power of @ObservedObject, @Published and @State.

理解概念的粗略示例:

import SwiftUI

struct ContentView: View {
    @ObservedObject var handler = Handler()
    var body: some View {
        Button(action: { self.handler.toggleShowAlert() }) { Text("Click") }
            .alert(isPresented: $handler.shouldShowAlert) {
                Alert(title: Text(handler.someTitle),
                    message: Text(handler.someMessage),
              dismissButton: .default(Text("Close")))
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

class Handler: ObservableObject {
    @Published var shouldShowAlert: Bool = false
    @Published var someTitle = ""
    @Published var someMessage = ""

    func toggleShowAlert() {
        shouldShowAlert.toggle()
        someTitle = "ErrorTitle"
        someMessage = "ErrorMessage"
    }
}

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