Exploring the tracking options in view level code.

Tracker+SwiftUI.swift

import SwiftUI

// MARK: -  SwiftUI environment definition (CoreTracking)

private struct EmptyTracker: Tracker {
    func track(_ event: Event) {}
}

public struct TrackerEnvironmentKey: EnvironmentKey {
    public static let defaultValue: Tracker = EmptyTracker()
}

extension EnvironmentValues {

    public var tracker: Tracker {
        get { self[TrackerEnvironmentKey.self] }
        set { self[TrackerEnvironmentKey.self] = newValue }
    }
}

// MARK: - On appear tracker view modifier (CoreTracking)

private struct OnAppearTracker: ViewModifier {

    @Environment(\.tracker) private var tracker
    let event: Event

    func body(content: Content) -> some View {
        content.onAppear { tracker.track(event) }
    }
}

extension View {

    public func onAppear(track event: Event) -> some View {
        modifier(OnAppearTracker(event: event))
    }
}

// MARK: - Tracking event definition (FeatureKit)

public struct AmazingViewDidAppear: Event {}

extension Event where Self == AmazingViewDidAppear {
    public static var amazingViewDidAppear: AmazingViewDidAppear { AmazingViewDidAppear() }
}

// MARK: - View code (FeatureUI)

struct AmazingView: View {

    var body: some View {
        Text("Hello world")
            .onAppear(track: .amazingViewDidAppear)
    }
}

Tracker+UIKit.swift

// This uses the responder chain to allow parent responders to supply the tracker to their children.

import UIKit

// MARK: -  UIKit responder definition (CoreTracking)

// Unfortunate hack neccessary to allow tracker to be defined on UIResponder and overridden in the app delegate.
public class ObjectiveCTracker: NSObject, Tracker {

    private let tracker: Tracker
    public init(tracker: Tracker) {
        self.tracker = tracker
    }

    public func track(_ event: Event) {
        tracker.track(event)
    }

}

extension UIResponder {

    @objc open var tracker: ObjectiveCTracker {
        next?.tracker ?? ObjectiveCTracker(tracker: EmptyTracker())
    }
}

// MARK: - Tracker definition (Main App)

final class AppDelegate: UIResponder {

    override var tracker: ObjectiveCTracker {
        ObjectiveCTracker(tracker: CompositeTracker(trackers: [
            // segment
            // internal logger
        ]))
    }
}

// MARK: - Usage from view controller

final class AmazingViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        tracker.track(.amazingViewDidAppear)
    }
}