Singleton network check

NSString *const networkStateChanged = @"networkStateChanged";

@implementation AppState

SYNTHESIZE_SINGLETON_FOR_CLASS(AppState)

- (void)startNetworkCheck {
    if(!self.reachability) {
        
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(reachabilityChanged:)
                                                     name:kReachabilityChangedNotification
                                                   object:nil];
        
        self.reachability = [Reachability reachabilityWithHostname:@"www.google.com"];
        [self.reachability startNotifier];
    }
}

- (void)reachabilityChanged:(NSNotification*)note
{
	Reachability* r = [note object];
	NetworkStatus ns = r.currentReachabilityStatus;
	
    BOOL tmpNetworkState = self.isConnected;
    
	if (ns == NotReachable) {
		self.isConnected = NO;
        DDLogInfo(@"reachabilityChanged NOT connected");
	} else {
		self.isConnected = YES;
        DDLogInfo(@"reachabilityChanged CONNECTED");
	}

    if(tmpNetworkState != self.isConnected) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [[NSNotificationCenter defaultCenter] postNotificationName:networkStateChanged object:nil];
        });
    }
}

- (BOOL)hasNetwork {
    return self.isConnected;
}