Check internet Reachability iOS 12+

Appdelegate.swift

import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        Reachability.shared.startNetworkReachabilityObserver()
        return true
    }
}

NotificationName.swift

import Foundation

protocol NotificationName {
    var name: Notification.Name { get }
}

extension RawRepresentable where RawValue == String, Self: NotificationName {
    var name: Notification.Name {
        return Notification.Name(rawValue)
    }
}

enum Notifications {
    enum Reachability: String, NotificationName {
        case connected
        case notConnected
    }
}

Presenter.swift

// Check internet connection   
if Reachability.shared.isConnected {
       print("no internet connection")   
 }

// Observe internet connection   
 [Notifications.Reachability.connected.name,
  Notifications.Reachability.notConnected.name].forEach { (notification) in
            NotificationCenter.default.addObserver(self, selector: #selector(changeInternetConnection), name: notification, object: nil)
  }

    @objc
    private func changeInternetConnection(notification: Notification) {
        if notification.name == Notifications.Reachability.notConnected.name {
            showError(title: Strings.noInternetConnectionTitle.localized())
        }
    }

Reachability.swift

import Network
import Foundation

class Reachability {

    static var shared = Reachability()
    lazy private var monitor = NWPathMonitor()

    var isConnected: Bool {
        return monitor.currentPath.status == .satisfied
    }

    func startNetworkReachabilityObserver() {
        monitor.pathUpdateHandler = { path in
            if path.status == .satisfied {
                NotificationCenter.default.post(name: Notifications.Reachability.connected.name, object: nil)
            } else if path.status == .unsatisfied {
                NotificationCenter.default.post(name: Notifications.Reachability.notConnected.name, object: nil)
            }
        }
        let queue = DispatchQueue.global(qos: .background)
        monitor.start(queue: queue)
    }
}