Face ID

Overview

The LocalAuthentication package supports authentication in iOS apps using either Face ID or Touch ID.

Setup

Select the top entry in the Navigator.
Under “TARGETS”, select the app target.
Click the “Info” tab.
Click the ”+” button to the right of the last key in the table.
Enter the key “Privacy - Face ID Usage Description”.
Enter a value that describes why Face ID is being used such as “We want to ensure that only you can view your data.”

Implementation

In the main view of the app add import LocalAuthentication

Add the following:

@State private var authenticated = false

func authenticate() {
    let context = LAContext()
    var error: NSError?

    if context.canEvaluatePolicy(
        .deviceOwnerAuthenticationWithBiometrics,
        error: &error
    ) {
        let reason = "We want to ensure that only you can see your data."
        context.evaluatePolicy(
            .deviceOwnerAuthenticationWithBiometrics,
            localizedReason: reason
        ) { success, error in
            if success {
                authenticated = true
            } else {
                // The user did not authenticate.
            }
        }
    } else {
        // The device does not support biometrics.
    }
}

Add a call to onAppear to the top View returned by the body that calls the authenticate function.
```
.onAppear {
    authenticate()
}
```
Use the value of authenticated to decide what to render.
Provide an alternate way for users to authenticate such as entering a username and password in case there are reasons they cannot currently use Face ID.

Testing in Simulator

To test in the Simulator, open the Simulator app and select Features … Face ID … Enrolled.

To simulate a successful Face ID scan, select Features … Face ID … Matching Face.

To simulate an unsuccessful Face ID scan, select Features … Face ID … Non-matching Face.