Observer network with Reachablity

observe_network.m

- (void)reachabilityChanged:(NSNotification *)note 
{
    Reachability* curReach = [note object];
    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
    NetworkStatus status = [curReach currentReachabilityStatus];
    
    if (status == NotReachable) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil
                                                        message:@"当前没有可用网络"
                                                       delegate:nil
                                              cancelButtonTitle:@"YES" otherButtonTitles:nil];
        [alert show];
        [alert release];
    }
}

- (void)observeNetwork
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(reachabilityChanged:)
                                                 name: kReachabilityChangedNotification
                                               object: nil];
    Reachability *hostReach = [[Reachability reachabilityWithHostName:@"www.google.com"] retain];
    [hostReach startNotifier];   
    [hostReach release];
}