func startupTimeReceived(_ data: StartupTimeData) { ... }

func fatalHangReceived(info: HangInfo) { ... }

func nonFatalHangReceived(info: HangInfo) { ... }

func viewControllerLeakReceived(viewController: UIViewController) { ... }

func watchdogTerminationReceived(_ data: WatchdogTerminationData) { ... }

func appRenderingMetricsReceived(metrics: RenderingMetrics) { ... }

func screenIdentifier(for viewController: UIViewController) -> ScreenIdentifier? { ... }

func ttiMetricsReceived(metrics: TTIMetrics, screen: ScreenIdentifier) { ... }

func renderingMetricsReceived(metrics: RenderingMetrics, screen: ScreenIdentifier) { ... }

let metricsConsumer = MetricsConsumer()
try PerformanceMonitoring.enable(config: .all(receiver: metricsConsumer))

// or with more flexibility

let metricsConsumer = MetricsConsumer()
let config: Config = [
    .screenLevelTTI(metricsConsumer),
    .screenLevelRendering(metricsConsumer),
    .appLevelRendering(metricsConsumer),
    .hangs(metricsConsumer),
]
try PerformanceMonitoring.enable(
    config: config,
    // you may pass your own key-value storage
    storage: KeyValueStorage.default,
    // you may pass a flag if app did crash from Crashlytics
    didCrashPreviously: didCrashPreviously
)

// We define enum with all our possible screens
// If you have too many screens, there can be several enums, 
// or just a string identifier.
enum PerformanceScreen: String {
    case search
    case details
    case checkout
}

// We define a protocol for screens to conform
protocol PerformanceTrackableScreen {
    var performanceScreen: PerformanceScreen? { get }
}

// For view controllers it is easy, we just return which screen is this
extension SearchViewController: PerformanceTrackableScreen {
    var performanceScreen: PerformanceScreen? { .search  }
}

// If you have SwiftUI screens without corresponding custom `UIHostingController`, 
// you will need to add introspection logic to find root views 
// in any `UIHostingController` in the app.
//
// We should conform to this protocol in the topmost view of the screen.
//
// NB: if possible, better to use your own subclass for `UIHostingController`
// and implement `PerformanceTrackableScreen` only in your subclass.
// Otherwise it may be additional performance overhead to introspect 
// all hosting controllers in the app
extension CheckoutScreenSwiftUIView: PerformanceTrackableScreen {
    var performanceScreen: PerformanceScreen? { .checkout }
}

// We also need to implement the protocol in UIHostingController,
// So we can determine which is the SwiftUI view inside this controller.
extension UIHostingController: PerformanceTrackableScreen {
    var performanceScreen: PerformanceScreen? {
        return (introspectRootView() as? PerformanceTrackableScreen)?.performanceScreen
    }
}

// In our metrics consumer we will receive UIViewController 
// and should determine which screen is this.
class MetricsConsumer: TTIMetricsReceiver {
    func screenIdentifier(for viewController: UIViewController) -> PerformanceScreen? {
        (viewController as? PerformanceTrackableScreen)?.performanceScreen
    }

    func ttiMetricsReceived(metrics: TTIMetrics, screen: PerformanceScreen) {
        // send the event to your backend with this identifier
        send(metric: "tti", value: metrics.tti.seconds, screen: performanceScreen.rawValue)
    }
}