ReachabilityManager - Using https://github.com/ashleymills/Reachability.swift, updated for Swift 4.2

ReachabilityManager.swift

import Foundation
import Reachability

class ReachabilityManager: NSObject {

    static let shared = ReachabilityManager()

    var isNetworkAvailable: Bool {
        return reachabilityStatus != .none
    }

    var reachabilityStatus: Reachability.Connection = .none
    let reachability = Reachability()


    @objc func reachabilityChanged(_ notification: Notification) {
        if let reachability = notification.object as? Reachability {
            switch reachability.connection {
            case .none:
                debugPrint("Network became unreachable")
            case .wifi:
                debugPrint("Network reachable through WiFi")
            case .cellular:
                debugPrint("Network reachable through Cellular Data")
            }
        } else {
            debugPrint("ReachabilityManager - Unrecognized notification object")
        }
    }

    func startMonitoring() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(reachabilityChanged(_:)),
                                               name: Notification.Name.reachabilityChanged,
                                               object: reachability)
        do {
            try reachability?.startNotifier()
        } catch {
            debugPrint("Could not start reachability notifier")
        }
    }

    func stopMonitoring() {
        reachability?.stopNotifier()
        NotificationCenter.default.removeObserver(self, name: Notification.Name.reachabilityChanged,
                                                  object: reachability)
    }
}