使用swiftUI进行生物识别身份验证评估

Question

我已经能够在我的应用程序中获得Face/Touch ID的初级版本。但是，我想添加更好的回退和错误处理。

所以我一直在研究如何做到这一点。有这样的奇妙资源：

人脸识别评估过程工作不正常

然而，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：

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

和

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

任何帮助都将不胜感激。非常感谢。

这是我在AuthenticateView.swift 中的代码

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)
}

Answer 1

说明：

"已知"只能应用于类和类绑定协议类型，而不能应用于"AuthenticateView">

首先，您有AuthenticateView，它是struct。你不能做class，因为整个苹果的SwiftUI理念都是关于结构的。因为Struct是值类型，而不是引用类型，所以没有这样的指针。因此，您可能不会在struct AuthenticateView: View {}中包含包含unowned self和weak self修饰符的代码部分

类型为"AuthenticateView"的值没有成员"present">

present是UIViewController的方法。在SwiftUI中，您无法访问它。警报将使用下一种样式显示：

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")))
}
}
}

解决方案：对于您的情况，我将为您的逻辑创建ObservableObject的classHandler子类，并使用@ObservedObject、@Published和@State的功能。

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"
}
}