iphone - connection recovered callback - iphone

Question

I would like to know if there's an automatic way of knowing when the connection was recovered.
My app connects to a webservice, lets say the network is not available in that moment so the app won't get the info from the server, but I would like the app to automactily try to reconect to the server if it "feels" that the connection was recovered.
Is there such a callback?

Answer 1

In whatever class you handle your NSURLConnection you need to add some connection check. So below I have posted an example
Create a Reachability instance
Add an observer to the Reachability did change notification
When the connection will change the - (void)networkReachabilityDidChange:(NSNotification *)notification will be fired.
You obviously check the networkStatus before firing off a connection in the first place.
-(id)init
{
self = [super init];
if(self)
{
Reachability* newInternetReachability = [Reachability reachabilityForInternetConnection];
[newInternetReachability startNotifier];
self.networkReachability = newInternetReachability;
networkStatus = [self.networkReachability currentReachabilityStatus];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(networkReachabilityDidChange:) name:kReachabilityChangedNotification object:nil];
}
return self;
}
- (void) startHTTPRequest
{
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:YOUR_URL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:YOUR_REQUEST_TIMEOUT];
NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest: delegate:self];
}
- (void)networkReachabilityDidChange:(NSNotification *)notification
{
Reachability *currReach = [notification object];
NSParameterAssert([currReach isKindOfClass: [Reachability class]]);
int currStatus = [currReach currentReachabilityStatus];
// Check that current reachability is not the same as the old one
if(currReach != self.networkReachability)
{
switch (currStatus) {
case ReachableViaWiFi:
// fire off connection
[self startHTTPRequest];
break;
case ReachableViaWWAN:
// Fire off connection (3G)
[self startHTTPRequest];
break;
case NotReachable:
// Don't do anything internet not reachable
break;
default:
break;
}
[self updateReachability];
}
This is only a simple example but you probably need to persist the request until the connection has become available so you can fire it off later. This could be done via NSOperationQueue or something similar.

Answer 2

There isn't such a thing from the standard library perspective. You will have to implement that yourself. You could use apple's Reachability code to listen for network changes. So once you receive a notification from the Reachability code saying that the internet is now connected, you could fire off an URL connection. If you need an example I could mock something up quickly for you.