Reachability code blocking main thread

I'm currently working on开发者_如何学编程 an app that requires me to check for reachability.

Owing to that, I started looking stuff up and found DDG and Apple's code. I decided to go with Apple's latest reachability code.

I imported that, and as suggested in Apple's sample, I came up with the following way to register:

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

    //check for local connection and start notifier
    client = [[Reachability reachabilityForInternetConnection] retain];
    [client startNotifier];

    //check for server connection and start notifier
    server = [[Reachability reachabilityWithHostName:SERVER_HOST_NAME] retain];
    [server startNotifier];

    //check for other server and start notifier
    otherServer = [[Reachability reachabilityWithHostName:OTHER_SERVER_HOST_NAME] retain];
    [otherServer startNotifier];

What I observed when I ran the app was that this code started blocking the UI (blocking the main thread). I could not interact with other UI elements till the host name was resolved. Now I know that Apple has stated a warning about DNS resolution and making it asynchronous.

My question would be, how do I go ahead and make it asynchronous?

Do I spawn another thread and keep it running so as to not "release" the Reachability object?

Thanks in advance for your help! :)

Okay. Well, I found out what the problem was. >_<

The code posted above does indeed work asynchronously.

However, the code that I had written under notificationHandler: was making a synchronous call to a service. It was written by someone else, owing to which it took me some time to figure out that that was the source of the UI freeze. However, problem has been solved. I thought I'd write this post so as to give a closure to this question. :)

Thanks again!