Detecting Network Connectivity Changes using Reach

问题:

I'm trying to integrate network connectivity detection into my app, however it seems that somewhere along the line I have made a mistake as my network changes are not being detected/printed out into the console.

As mentioned in the post, I'm currently using these following classes and tools for the job:

1. Reachability {.h, .m}
2. NSNotificationCenter
3. Network Link Conditioner

Code

In the AppDelegate.Swift, I've set up the NSNotificationCenter to detect changes:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// ... 
// A: Checks if the device is connected to the internet

    var defaultCenter: Void = NSNotificationCenter().addObserver(self, selector:"checkForReachability", name: kReachabilityChangedNotification, object: nil)

}

In the same class AppDelegate, I've also created this function to be triggered whenever there is a change:

func checkForReachability () {

    var networkReachability = Reachability.reachabilityForInternetConnection()
    networkReachability.startNotifier()

    var remoteHostStatus = networkReachability.currentReachabilityStatus()
    if (remoteHostStatus.value == NotReachable.value) {
        println("Not Reachable")
    } else if (remoteHostStatus.value == ReachableViaWiFi.value) {
        println("Reachable via Wifi")
    } else {
        println("Reachable")
    }
}

However, when using the Network Link Conditioner to manipulate and simulate changes in conditions, I haven't been able to see any of those changes reflected in the console. Any help would be swell!

回答1:

You must create a Reachability object before you can receive notifications from it. Also, be sure to call the startNotifier() method on the Reachability object you create. This would be an example of how to do so inside of your application delegate:

class AppDelegate: UIResponder, UIApplicationDelegate
{
    private var reachability:Reachability!;

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool
    {
        NSNotificationCenter.defaultCenter().addObserver(self, selector:"checkForReachability:", name: kReachabilityChangedNotification, object: nil);

        self.reachability = Reachability.reachabilityForInternetConnection();
        self.reachability.startNotifier();
    }

    @objc func checkForReachability(notification:NSNotification)
    {
        // Remove the next two lines of code. You cannot instantiate the object
        // you want to receive notifications from inside of the notification
        // handler that is meant for the notifications it emits.

        //var networkReachability = Reachability.reachabilityForInternetConnection()
        //networkReachability.startNotifier()

        let networkReachability = notification.object as Reachability;
        var remoteHostStatus = networkReachability.currentReachabilityStatus()

        if (remoteHostStatus.value == NotReachable.value)
        {
            println("Not Reachable")
        }
        else if (remoteHostStatus.value == ReachableViaWiFi.value)
        {
            println("Reachable via Wifi")
        }
        else
        {
            println("Reachable")
        }
    }
}

I recommend you take a look at the documentation for NSNotificationCenter and NSNotification. That way you'll be more familiar with how to work with notifications next time something like this comes up.

Swift 3

NotificationCenter.default.addObserver(self, selector:Selector(("checkForReachability:")), name: NSNotification.Name.reachabilityChanged, object: nil)
let reachability: Reachability = Reachability.forInternetConnection()
reachability.startNotifier()

回答2:

Updated for Swift 4 / Swift 5 according @Hardik.T

1. Import Reachability.swift file from https://github.com/ashleymills/Reachability.swift/archive/master.zip in your XCode project

2. Create a new Swift class : ConnectionManager.swift

class ConnectionManager {

static let sharedInstance = ConnectionManager()
private var reachability : Reachability!

func observeReachability(){
    self.reachability = Reachability()
    NotificationCenter.default.addObserver(self, selector:#selector(self.reachabilityChanged), name: NSNotification.Name.reachabilityChanged, object: nil)
    do {
        try self.reachability.startNotifier()
    }
    catch(let error) {
        print("Error occured while starting reachability notifications : \(error.localizedDescription)")
    }
}

@objc func reachabilityChanged(note: Notification) {
    let reachability = note.object as! Reachability
    switch reachability.connection {
    case .cellular:
        print("Network available via Cellular Data.")
        break
    case .wifi:
        print("Network available via WiFi.")
        break
    case .none:
        print("Network is not available.")
        break
    }
  }
}

3. Use it in your AppDelegate file :

func application(_ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    ConnectionManager.sharedInstance.observeReachability()
    return true
}

回答3:

Instead of polluting the AppDelegate.swift with observer callbacks I would recommend adding observers only into the relevant view controllers.

AppDelegate.swift

import ReachabilitySwift


@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate
{
    var reachability: Reachability?


    func application( _ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]? ) -> Bool
    {
       self.reachability = Reachability()

       do
       {
          try reachability?.startNotifier()
       }
       catch
       {
          print( "ERROR: Could not start reachability notifier." )
       }

       return true
    }


    class func sharedAppDelegate() -> AppDelegate?
    {
        return UIApplication.shared.delegate as? AppDelegate
    }


    // Remaining functions
}

Example of a ViewController:

class ExampleVC: UIViewController
{
    override func viewDidLoad()
    {
        // Add reachability observer
        if let reachability = AppDelegate.sharedAppDelegate()?.reachability
        {
            NotificationCenter.default.addObserver( self, selector: #selector( self.reachabilityChanged ),name: ReachabilityChangedNotification, object: reachability )
        }
    }


    @objc private func reachabilityChanged( notification: NSNotification )
    {
        guard let reachability = notification.object as? Reachability else
        {
            return
        }

        if reachability.isReachable
        {
            if reachability.isReachableViaWiFi
            {
                print("Reachable via WiFi")
            }
            else
            {
                print("Reachable via Cellular")
            }
        }
        else
        {
            print("Network not reachable")
        }
    }
}

回答4:

Upadated for swift 2.1 & XCode 7:

try this third party Highly Rated Reachablity Class

 func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool
    {
 // Allocate a reachability object
        self.reach = Reachability.reachabilityForInternetConnection()

        // Tell the reachability that we DON'T want to be reachable on 3G/EDGE/CDMA
        self.reach!.reachableOnWWAN = false

        // Here we set up a NSNotification observer. The Reachability that caused the notification
        // is passed in the object parameter
        NSNotificationCenter.defaultCenter().addObserver(self,
            selector: "reachabilityChanged:",
            name: kReachabilityChangedNotification,
            object: nil)

        self.reach!.startNotifier()

return true
}

//Reachbality Notification Response

    func reachabilityChanged(notification: NSNotification) {
        if self.reach!.isReachableViaWiFi() || self.reach!.isReachableViaWWAN() {
            print("Service avalaible!!!")
        } else {
            print("No service avalaible!!!")

            AppHelper.showALertWithTag(0, title: constants.AppName.rawValue, message: "Please Check Your Internet Connection!", delegate: self, cancelButtonTitle: "OK", otherButtonTitle: nil)
        }
    }

回答5:

Updated A. R. Younce answer for Swift 2:

func checkForReachability(notification:NSNotification) {
    if let networkReachability = notification.object as? Reachability {
        let remoteHostStatus = networkReachability.currentReachabilityStatus()

        if (remoteHostStatus == NotReachable) {
            print("Not Reachable")
        }
        else if (remoteHostStatus == ReachableViaWiFi) {
            print("Reachable via Wifi")
        }
        else {
            print("Reachable")
        }
    } else {
        print("Unknown")
    }
}

回答6:

Based on this open source solution Wrapped to class

Swift 5

import Foundation

final class ReachabilityHandler {

  private var reachability: Reachability? = Reachability()

  // MARK: - LifeCycle

  init() {
    configure()
  }

  deinit {
    NotificationCenter.default.removeObserver(self)
    reachability?.stopNotifier()
  }

  // MARK: - Private

  private func configure() {
    NotificationCenter.default.addObserver(self,
                                           selector: #selector(ReachabilityHandler.checkForReachability(notification:)),
                                           name: Notification.Name.reachabilityChanged,
                                           object: nil)
    try? reachability?.startNotifier()

  }

  @objc private func checkForReachability(notification: NSNotification) {
    let networkReachability = notification.object as? Reachability
    if let remoteHostStatus = networkReachability?.connection {
      switch remoteHostStatus {
        case .none:

        case .wifi,
             .cellular:

      }
    }
  }
}

In AppDelegate

class AppDelegate: UIResponder, UIApplicationDelegate {

  private var rechabilityObserver: ReachabilityHandler?

  var window: UIWindow?

  // MARK: - LifeCycle

  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    rechabilityObserver = ReachabilityHandler()

    return true
  }
}

回答7:

Swift 2.0 - Check Network Using Reachability, NSNotification

AppDelegate.swift

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool 
{
    NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(self.checkNetworkStatus(_:)), name: "ReachabilityChangedNotification", object: nil);

    do{self.reachability = try Reachability.reachabilityForInternetConnection()}catch{}
    do{try self.reachability.startNotifier()}catch{}
    self.checkNetworkStatus()

    return true
}

Declare networkStatus variable

var networkStatus : Reachability.NetworkStatus!

checkNetworkStatus() Function

func checkNetworkStatus()
{
    networkStatus = reachability.currentReachabilityStatus

    if (networkStatus == Reachability.NetworkStatus.NotReachable)
    {
        print("Not Reachable")
    }
    else
    {
        print("Reachable")
    }
}

OtherClass.Swift

let delegate = UIApplication.sharedApplication().delegate as! AppDelegate

if (delegate.networkStatus!=Reachability.NetworkStatus.NotReachable)
{
   // Call Webservice     
}
else
{
   delegate.checkNetworkStatus()  //Not Reachable print  
}

回答8:

1) Install pod or add ReachabilitySwift in your project

2) in AppDelegate.swift

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(self.checkForReachability(_:)), name: "ReachabilityChangedNotification", object: nil);

        do {
            try self.reachability = Reachability.reachabilityForInternetConnection()
        }
        catch {
            print(error)
        }

        do {
            try self.reachability.startNotifier()
        }
        catch {
            print(error)
        }

        return true
    }

3)

func checkForReachability(notification:NSNotification) {
        let networkReachability = notification.object as! Reachability;
        let remoteHostStatus = networkReachability.currentReachabilityStatus

        if (remoteHostStatus == .NotReachable) {
            print("Not Reachable")
        }
        else if (remoteHostStatus == .ReachableViaWiFi || remoteHostStatus == .ReachableViaWWAN) {
            print("Reachable via Wifi or via WWAN")
        }
    }

回答9:

Using ReachabilitySwift framework which is a replacement for Apple's Reachability re-written in Swift with closures

1. Install ReachabilitySwift Cocoapod

2. Create NetworkReachability wrapper class for observing the reachability changes

   import ReachabilitySwift

   extension Notification.Name {
       static let ReachabilityStatusChanged = Notification.Name("ReachabilityStatusChangedNotification")
   }
   
   //MARK: NetworkReachability
   
   final class NetworkReachability {
   
   enum ReachabilityStatus: Equatable {
       case connected
       case disconnected
   }
   
   static let shared = NetworkReachability()
   
   private let reachability = try! Reachability()
   
   var reachabilityObserver: ((ReachabilityStatus) -> Void)?
   
   private(set) var reachabilityStatus: ReachabilityStatus = .connected
   
   private init() {
       setupReachability()
   }
   
   /// setup observer to detect reachability changes
   private func setupReachability() {
       let reachabilityStatusObserver: ((Reachability) -> ()) = { [unowned self] (reachability: Reachability) in
           self?.updateReachabilityStatus(reachability.connection)
       }
       reachability.whenReachable = reachabilityStatusObserver
       reachability.whenUnreachable = reachabilityStatusObserver
   }
   
   /// Start observing reachability changes
   func startNotifier() {
       do {
           try reachability.startNotifier()
       } catch {
           print(error.localizedDescription)
       }
   }
   
   
   /// Stop observing reachability changes
   func stopNotifier() {
       reachability.stopNotifier()
   }
   
   
   /// Updated ReachabilityStatus status based on connectivity status
   ///
   /// - Parameter status: Reachability.Connection enum containing reachability status
   private func updateReachabilityStatus(_ status: Reachability.Connection) {
       switch status {
           case .unavailable, .none:
               notifyReachabilityStatus(.disconnected)
           case .cellular, .wifi:
               notifyReachabilityStatus(.connected)
       }
   }
   
   
   /// Notifies observers about reachability status change
   ///
   /// - Parameter status: ReachabilityStatus enum indicating status eg. .connected/.disconnected
   private func notifyReachabilityStatus(_ status: ReachabilityStatus) {
       reachabilityStatus = status
       reachabilityObserver?(status)
       NotificationCenter.default.post(
           name: Notification.Name.ReachabilityStatusChanged,
           object: nil,
           userInfo: ["ReachabilityStatus": status]
       )
   }
   
   /// returns current reachability status
   var isReachable: Bool {
       return reachability.connection != .unavailable
   }
   
   
   /// returns if connected via cellular or wifi
   var isConnectedViaCellularOrWifi: Bool {
       return isConnectedViaCellular || isConnectedViaWiFi
   }
   
   /// returns if connected via cellular
   var isConnectedViaCellular: Bool {
       return reachability.connection == .cellular
   }
   
   /// returns if connected via cellular
   var isConnectedViaWiFi: Bool {
       return reachability.connection == .wifi
   }
   
   deinit {
       stopNotifier()
   } 
   

   }

   in AppDelagete.Swift

   func application(_ application: UIApplication,
                        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    NetworkReachability.shared.startNotifier()
    reahabilityObserver()
   }
   
   func reachabilityObserver() {
   
     NetworkReachability.shared.reachabilityObserver = { [weak self] status in
           switch status {
               case .connected:
                   print("Reachability: Network available