iOS Tutorial Use Face ID Touch ID and Passcode

This is a short tutorial/code snippet on how to successfully implement Touch ID in your app.
Thanks to @Semen Matusovskiy for his code.

You need this OBJC Code
#import <LocalAuthentication/LocalAuthentication.h>
- (void) authenticateButtonTapped
   __result = -1; 
   LAContext *context = [[LAContext alloc] init];
   NSError *error = nil;
   if ([context canEvaluatePolicy: LAPolicyDeviceOwnerAuthentication error: &error])
       [context evaluatePolicy: LAPolicyDeviceOwnerAuthentication localizedReason: @"Are you the device owner?" reply: ^(BOOL success, NSError *error)
           if (error) { __result = 2; return; };
           if (success) { __result = 0; } else { __result = 1; };
       { __result = 3; };
#End If
Call it with this:
    Dim no As NativeObject = B4XPages.GetManager.GetTopPage.B4XPage 'if you dont use B4XPages then use "Me"
    no.RunMethod ("authenticateButtonTapped", Null)
    Do While result < 0
        Sleep (50)
    Select Case result
        Case 0
            xui.MsgboxAsync ("Success: You are the device owner", "B4X")
        Case 1
            xui.MsgboxAsync ("Error: You are not the device owner", "B4X")
        Case 2
            xui.MsgboxAsync ("Error: There was a problem verifying your identity", "B4X")
        Case 3
            xui.MsgboxAsync ("Error: Your device cannot authenticate using TouchID", "B4X")
    End Select

This code asks for the Face ID, if this fails, then you have the choice to enter your pin code.

Alexander Stolte

Licensed User
Longtime User
If you only want FaceID with the option for your own Pincode then replace "LAPolicyDeviceOwnerAuthentication" with "LAPolicyDeviceOwnerAuthenticationWithBiometrics" then you can use your own pincode system.

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