Question

I am using ASIHTTPRequest. I need to know how to do the following events using it;

The following are the way i should be checking for the availability of the internet, but in which event should i add it to address the following issues;

self.remoteHostStatus           = [[Reachability sharedReachability] remoteHostStatus];
self.internetConnectionStatus   = [[Reachability sharedReachability] internetConnectionStatus];
self.localWiFiConnectionStatus  = [[Reachability sharedReachability] localWiFiConnectionStatus];

1.) Applications like foursquare pops out an alert as soon as the internet is lost ? How is this done, and in what event should i code this ? (The user might be performing a task, and suddenly the wifi goes off, then i should pop up a warning, saying no wifi available)

2.) As soon as the internet/wifi is back i need to refresh and update the data. How is this done? (it should be listening continuously, and once the internet is back it should update that view)

Answer 1

There is a notification posted by Reachability called kReachabilityChangedNotification.

You can enforce the generation of that notification by using Reachability’s

- (BOOL)startNotifier;
- (void)stopNotifier;

First register for that notification – for example in viewDidLoad of a UIViewController:

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

Add the following method – for example to your UIViewController implementation.

- (void)reachabilityChangedNotificationSent:(NSNotification *)notification
{
    NSLog(@"reachability changed: %@", notification.userInfo);
}

Now simply invoke startNotifier – for example in viewDidLoad again and you should be informed whenever any changes happen.

[[Reachability sharedReachability] startNotifier];

Do not forget to remove yourself from that notification and to invoke stopNotifier when done. Sticking to my example would mean that you should add this to your viewDidUnload implementation.

[[Reachability sharedReachability] stopNotifier];
[[NSNotificationCenter defaultCenter] removeObserver:self
                                                name:kReachabilityChangedNotification 
                                              object:nil];