iOS - Local authentication change fail message

Question

There's a LA service in my app that uses TouchID pretty much as usual. The problem is that I want to change what is written on the alert that shows up when touchId authentication is prompted. First it shows what I declare in reason string, than if auth fails, it only changes title to 'Repeat', but body stays the same.

Is there any chance to change the alert's body for a different message when auth fails? I tried changing reason string but no effect.

This project is created using Xamarin, but Objective-C/Swift code is also acceptable. Thanks in advance!

UPD: here's my code:

if (context.CanEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, out authError))
            {
                var myReason = new NSString("Use your finger to authenticate");

                replyHandler = new LAContextReplyHandler((success, error) =>
                {
                    InvokeOnMainThread(() =>
                    {
                        if (success)
                        {
                            Login();
                        }
                        else
                        {
                            myReason = new NSString("Nope try again");

                            switch ((long)error.Code)
                            {
                                case (long)LAStatus.TouchIDLockout: // 5 times wrong, TouchID is locked system-wide
                                    {
                                        var alert = new UIAlertView("Sorry", "Exceeded and blocked message", null, "OK");
                                        alert.Show();
                                        touchIdButton.Hidden = true;
                                    }
                                    break;
                                case (long)LAStatus.AuthenticationFailed: // 3 times wrong
                                    {
                                        var alert = new UIAlertView("Sorry", "Exceeded message", null, "OK");
                                        alert.Show();
                                        touchIdButton.Hidden = true;
                                    }
                                    break;
                                case (long)LAStatus.UserFallback: //Enter Passcode
                                    //no UserFallback for now
                                    break;
                            }

                        }
                    });
                });
                context.EvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, myReason, replyHandler);

Answer 1

No. There is no API for changing the Reason in between the auth process.

See https://developer.apple.com/documentation/localauthentication/lacontext/1514176-evaluatepolicy

localizedReason

The app-provided reason for requesting authentication, which displays in the authentication dialog presented to the user.

This means: What you are trying is not intended by Apple. The reason for requesting the auth stays the same independent from the failed try count. In other words: Your reason for requesting hasn't change after the first failed attempt.

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