How to Get Change in Network Connection Notification from iOS Reachability Class

Detecting Network Connectivity Changes using Reachability, NSNotification and Network Link Conditioner in Swift

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()

How to get notifications for Network change(Connect,Disconnect,Change)

Look at this official Apple documentation

Using Reachability you can recognize the type of your connection.

There is also a complete example on how detect the changes and the documentation is updated now for ARC.

I hope this can help you

How to detect change in network with Reachability?

Another possible solution is to add a NS Notification in "application didfinishlaunching":

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkForReachability) name:kReachabilityChangedNotification object:nil];

and in checkForReachability method do this:

    Reachability *reachability = [Reachability reachabilityForInternetConnection];
    [reachability startNotifier];

    NetworkStatus remoteHostStatus = [reachability currentReachabilityStatus];

    if(remoteHostStatus == NotReachable) {
        //Do something
    }
     else if (remoteHostStatus == ReachableViaWiFi) {
    // Do something
 }
    else{

// Else do something else
}

Wifi-Network Changed Notification

If you are using this Reachability files then its easy.
Add an Observer inside the viewWillAppear

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityDidChange:) name:kReachabilityChangedNotification object:nil];

And implement the observer method

- (void)reachabilityDidChange:(NSNotification *)notification {
    Reachability *reachability = (Reachability *)[notification object];

    if ([reachability isReachable] && [reachability isReachableViaWiFi]) {
        NSLog(@"Reachable via Wifi");
    } 
}

Updated

Add the following code inside the Network change completion block of your Reachability handler. By Sending the SCNetworkReachabilityFlag as a parameter to the method.

-(BOOL)isReachableViaWiFi :(SCNetworkReachabilityFlags)flags {

        // Check we're reachable
        if((flags & kSCNetworkReachabilityFlagsReachable))
        {
            // Check we're NOT on WWAN
            if((flags & kSCNetworkReachabilityFlagsIsWWAN))
            {
                return NO;
            }
            return YES;
        }
     return NO;
}

Internet connection status swift reachability

Declare this in AppDelegate / Vc

let reachability = Reachability()!

NotificationCenter.default.addObserver(self, selector: #selector(reachabilityChanged(note:)), name: .reachabilityChanged, object: reachability)
do{
  try reachability.startNotifier()
}catch{
  print("could not start reachability notifier")
}

//

when status is changed this method is called

@objc func reachabilityChanged(note: Notification) {

   let reachability = note.object as! Reachability

    switch reachability.connection {
     case .wifi:
         print("Reachable via WiFi")
     case .cellular:
         print("Reachable via Cellular")
     case .none:
         print("Network not reachable")
    }
}

//

to avoid crashes don't forget to un register

reachability.stopNotifier()
NotificationCenter.default.removeObserver(self, name: .reachabilityChanged, object: reachability)

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