iosswiftauthenticationtouch-idface-id

Face ID evaluation process not working properly


I'm trying to get if Face ID or Touch ID succeeded in the function below

func authenticate() -> Bool{

    let context = LAContext()
    var error: NSError?

    guard context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) else {
        return false
    }
    var returnValue = false
    let reason = "Face ID authentication"
    context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason) 
    {
        isAuthorized, error in
        guard isAuthorized == true else {
            return print(error)
        }
        returnValue = true
        print("success")
    }
    return returnValue        
}

but even when it succeeds with this code it skips the returnValue = true is passed later which results a false return. why does this happen? and how can I fix this code to make it work like it is suppose to?

the code above is from this link just in case this person was watching, thank you.


Solution

  • Working code of Touch ID & Face ID LocalAuthentication

    (swift 4.0 & 5.0+ Code)

    Note : Privacy - Face ID Usage Description key add in Info.plist

    Use

    self.Authenticate { (success) in
         print(success)
    }
    

    Local Authentication Function

    import LocalAuthentication
    
    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)
            }
        }
        
    }
    

    Handle Error Codes with Messages

    //MARK: TouchID error
    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.biometryNotAvailable.rawValue:
            strMessage = "TouchI or FaceID DNot Available"
            
        case LAError.Code.biometryNotEnrolled.rawValue:
            strMessage = "TouchID or FaceID Not Enrolled"
            
        case LAError.Code.biometryLockout.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
    }
    

    Show alert message

    //MARK: Show Alert
    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)
    }