BiometryType for iOS 8+

LAContext+BiometryType.swift

import LocalAuthentication

extension LAContext {
    /// BiometryType that works on iOS versions older than iOS 11.
    var compatBiometryType: BiometryType {
        var authError: NSError?
        guard canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &authError), authError == nil else { return .none }
        // On iOS 11 we can get the biometry type directly.
        if #available(iOS 11.0, *) {
            switch biometryType {
            case .faceID: return .faceID
            case .touchID: return .touchID
            case .none: return .none
            }
        }
        // On older versions it must be touchID.
        return .touchID
    }
}

/// The type of biometric authentication supported by the device.
enum BiometryType {
    /// The device supports Touch ID.
    case touchID
    /// The device supports Face ID.
    case faceID
    /// No biometry type is supported.
    case none
    
    /// The name of the biometrics technology (e.g. Face ID)
    var localizedDescription: String {
        switch self {
        case .faceID:
            return "Face ID"
        case .touchID:
            return "Touch ID"
        case .none:
            return ""
        }
    }
}