从iOS 12开始，NWPathMonitor取代了Reachability。用这个:

import Network


struct Internet {
 
 private static let monitor = NWPathMonitor()
 
 static var active = false
 static var expensive = false
 
 /// Monitors internet connectivity changes. Updates with every change in connectivity.
 /// Updates variables for availability and if it's expensive (cellular).
 static func start() {
  guard monitor.pathUpdateHandler == nil else { return }
  
  monitor.pathUpdateHandler = { update in
   Internet.active = update.status == .satisfied ? true : false
   Internet.expensive = update.isExpensive ? true : false
  }
  
  monitor.start(queue: DispatchQueue(label: "InternetMonitor"))
 }
 
}

在使用:

Internet.start()

if Internet.active {
 // do something
}
  
if Internet.expensive {
 // device is using Cellular data or WiFi hotspot
}

这里是我的解决方案swift 2.3与库(reach .swift)

进入你的Podfile并添加:

pod 'ReachabilitySwift', '~> 2.4' // swift 2.3

然后进入您的终端:

pod install

然后创建一个新的文件ReachabilityManager并添加下面的代码:

import Foundation
import ReachabilitySwift

enum ReachabilityManagerType {
    case Wifi
    case Cellular
    case None
}

class ReachabilityManager {
    static let sharedInstance = ReachabilityManager()

    private var reachability: Reachability!
    private var reachabilityManagerType: ReachabilityManagerType = .None


    private init() {
        do {
            self.reachability = try Reachability.reachabilityForInternetConnection()
        } catch {
            print("Unable to create Reachability")
            return
        }

        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ReachabilityManager.reachabilityChanged(_:)),name: ReachabilityChangedNotification,object: self.reachability)
        do{
            try self.reachability.startNotifier()
        }catch{
            print("could not start reachability notifier")
        }
    }

    @objc private func reachabilityChanged(note: NSNotification) {

        let reachability = note.object as! Reachability

        if reachability.isReachable() {
            if reachability.isReachableViaWiFi() {
                self.reachabilityManagerType = .Wifi
            } else {
                self.reachabilityManagerType = .Cellular
            }
        } else {
            self.reachabilityManagerType = .None
        }
    }
}

extension ReachabilityManager {

    func isConnectedToNetwork() -> Bool {
        return reachabilityManagerType != .None
    }

}

如何使用:

进入你的AppDelegate.swift并添加下面的代码:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
     ReachabilityManager.sharedInstance
}

然后，当你想检查设备是否连接到互联网时，请:

if ReachabilityManager.sharedInstance.isConnectedToNetwork() {
   // Connected
} else {
  // Not connected
}

如果你正在使用Alamofire，你可以这样做:

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
configuration.timeoutIntervalForRequest = 15 //Set timeouts in sec
configuration.timeoutIntervalForResource = 15

let alamoFireManager = Alamofire.Manager(configuration:configuration)
alamoFireManager?.request(.GET, "https://yourURL.com", parameters: headers, encoding: .URL)
                     .validate()
                              .responseJSON { response in

                                if let error = response.result.error {
                                   switch error.code{
                                    case -1001:
                                        print("Slow connection")
                                        return
                                    case -1009:
                                        print("No Connection!")
                                        return
                                    default: break
                                    }
                                }

struct Connectivity {
    static let sharedInstance = NetworkReachabilityManager()!
    static var isConnectedToInternet:Bool {
        return self.sharedInstance.isReachable
    }
}

现在叫它

if Connectivity.isConnectedToInternet{
    call_your_methods_here()
} else{
    show_alert_for_noInternet()
}

如果有人已经在使用Alamofire，那么-

struct Connectivity {
  static let sharedInstance = NetworkReachabilityManager()!
  static var isConnectedToInternet:Bool {
      return self.sharedInstance.isReachable
    }
}

用法:

if Connectivity.isConnectedToInternet {
     print("Connected")
 } else {
     print("No Internet")
}

Swift 5.5, iOS 12+，没有更多的第三方库。

请检查这个要点https://gist.github.com/dimohamdy/5166ba6c88f6954fa6b23bc9f28cbe12

使用

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

Code

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)
    }
}