Application crashes when web service is down

how to handle when web service is down.

I loged in application and its Re-Directed to result screen.

When i turn off the web services my application is cr开发者_运维问答ashing.

How to handle this kind of issue

Here is the link to that file.

http://developer.apple.com/library/ios/#samplecode/Reachability/Listings/Classes_Reachability_h.html

to check for internet connectivity.

if you are using NSURLConnection then handle it in

     - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)err {
}