iOS - Face ID biometric integration

Question

I've integrated/implemented Face ID (Local Authentication) authentication for my app and everything works fine, except Face ID prompt Alert window interface.

It shows, a rounded square with a light gray background and the title "Face ID".

What should need to set for blank area exact above title? Is that space for face id icon? if yes then how can I set it? I've tried everything in LAContext and LAPolicy.

Look at this snapshot:

Here is my code:

    let laContext = LAContext()
    var error: NSError?
    let biometricsPolicy = LAPolicy.deviceOwnerAuthenticationWithBiometrics

    if (laContext.canEvaluatePolicy(biometricsPolicy, error: &error)) {

        if let laError = error {
            print("laError - \(laError)")
            return
        }

        var localizedReason = "Unlock device"
        if #available(iOS 11.0, *) {
            switch laContext.biometryType {
            case .faceID: localizedReason = "Unlock using Face ID"; print("FaceId support")
            case .touchID: localizedReason = "Unlock using Touch ID"; print("TouchId support")
            case .none: print("No Biometric support")
            }
        } else {
            // Fallback on earlier versions
        }


        laContext.evaluatePolicy(biometricsPolicy, localizedReason: localizedReason, reply: { (isSuccess, error) in

            DispatchQueue.main.async(execute: {

                if let laError = error {
                    print("laError - \(laError)")
                } else {
                    if isSuccess {
                        print("sucess")
                    } else {
                        print("failure")
                    }
                }

            })
        })
    }

Answer 1

That is only happen in simulator, in actual device the canvas is occupied by face icon animation.

The localizedReason is for only for Touch ID, since they both sharing the same API.

Update 1: Added screen recordings:

• iPhone X: https://youtu.be/lklRnLNHyQk
• iPhone 7: https://youtu.be/iIcduvD5JO0
• iPhone X Simulator: https://youtu.be/bOlRVLIND5c

They all ran the same code:

func beginFaceID() {

    guard #available(iOS 8.0, *) else {
        return print("Not supported")
    }

    let context = LAContext()
    var error: NSError?

    guard context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) else {
        return print(error)
    }

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

        print("success")
    }

}

Here is Working code for both TouchID & FaceID with all Error Codes (Swift 4)

https://stackoverflow.com/a/52093551/10150796