Question

I incorporated the Reachability Code into my app and its been successfully working for a few months but so far I’ve only used it on iOS 5 devices.
However it doesn’t work on an iOS 4 device.

The notification is registered for as follows:

 - (id) init
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(reachabilityChange:)
                                                 name:kReachabilityChangedNotification
                                               object:nil];

...


- (void) appBecameActive
{
...
self.reachability = [Reachability reachabilityWithHostName:[url host]];
...
[self.reachability startNotifier];

stopNotifier is only getting called in dealloc

The problem is the ReachabilityCallback isn’t getting called back when there is a reachabiity change, but I cannot see any reason why it should it ok on iOS5 but not iOS4.

This part of the code is unchanged from the Apple sample source code:

static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void *info) {
#pragma unused (target, flags)
  NSCAssert(info != NULL, @"info was NULL in ReachabilityCallback");
  NSCAssert([(__bridge id)info isKindOfClass:[Reachability class]], @"info was wrong class in ReachabilityCallback");

  Reachability *noteObject = (__bridge Reachability *)info;
  // Post a notification to notify the client that the network reachability changed.
  [[NSNotificationCenter defaultCenter] postNotificationName:kReachabilityChangedNotification object:noteObject];
}

As mentioned, everything has been working fine for a long time when running on iOS5 devices, has anybody else encountered a similar issue in the past incorporating the reachability code into with iOS4?

Answer 1

Edit the code in reachability that posts the notification to post it on the main thread, and see if that changes the behavior you’re seeing.

dispatch_async(dispatch_get_main_queue(), ^{ 
    [[NSNotificationCenter defaultCenter] postNotificationName:kReachabilityChangedNotification object:noteObject];
});

(assume you are listening for them on the main thread)