Sample implementation of AnalyticsManager. See the blogpost in Medium

AnalyticsManager.swift

import Foundation

final class AnalyticsManager: AnalyticsService {
    // MARK: - Properties -
    
    // The list of services added to this class as observers.
    internal private(set) var services = [AnalyticsService]()
    
    // MARK: - Singleton -
    static let instance = AnalyticsManager()
    private init() {}
    
    // MARK: - Methods -
    
    /**
     Adds a service as an observer.
     */
    func add(service: AnalyticsService) {
        self.services.append(service)
    }
 
    // MARK: - AnalyticsService -
    func initialize(application: UIApplication, launchOptions: [UIApplicationLaunchOptionsKey: Any]?) {
        // When AnalyticsManager is instantiated,
        // it also instantiates each service that 
        // has been added to it.
        for service in services {
            service.initialize(
                application     : application,
                launchOptions   : launchOptions
            )
        }
    }
    
    func track(event: Event) {
        // When an event is tracked by AnalyticsManager,
        // it will notify all the services that has been added to it.
        for service in services where service.shouldTrack(event: event) {
            service.track(event: event)
        }
    }
}