NSURLConnection sendSynchronousRequest data parsing crash

I am using sendSynchronousRequest and receiving data from a web server but the app is crashing while I am trying to parse the received data?

NSError *error;  
NSURLResponse *response;  
NSData *urlData=[NSURLConnection sendSynchronousRequest:req returningResponse:&response error:&error];  
NSString *data=[[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];   
NSLog(@"data received from url: %@", data); 
xmlParser = [[NSXMLParser alloc] initWithData: data];   
[xmlParser setDelegate: self];   
[xmlParser setShouldResolveExternalEntities:YES];   
[xmlParser parse];   
[xmlParser release];  

But after [xmlParser parse]; the app crashes. I am getting the following:

2011-03-01 09:36:31.735 MasterApp[228:207] -[NSCFString bytes]: unrecognized selector sent to instance 0x5f6b000  
2011-03-01 09:36:31.738 MasterApp[228:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString bytes]: unrecognized selector sent to instance 0x5f6b000'  
*** Call stack at first throw:  
(  
    0   CoreFoundation                      0x0252eb99 __exceptionPreprocess + 185  
    1   libobjc.A.dylib                     0x0267e40e objc_exception_throw + 47  
    2   CoreFoundation                      0x025306ab -[NSObject(NSObject)   doesNotRecognizeSelector:] + 187  
    3   CoreFoundation                      0x024a02b6 ___forwarding___ + 966  
    4   CoreFoundation                      0x0249fe72 _CF_forwarding_prep_0 + 50  
    5   Foundation                          0x00114afc -[NSXMLParser parse] + 147  
    6   MasterApp                           0x0000c731 -[identifierList getUrl] + 994  
    7   MasterApp                           0x0000c306 -[identifierList   actionSheet:clickedButtonAtIndex:] + 56  
    8   UIKit                               0x0077047d -[UIActionSheet(Private)   _buttonClicked:] + 258  
    9   UIKit                               0x002dc7f8 -[UIApplication   sendAction:to:from:forEvent:] + 119  
    10  UIKit                               0x00367de0 -[UIControl sendAction:to:forEvent:] + 67  
    11  UIKit                               0x0036a262 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527  
    12  UIKit                               0x00368e0f -[UIControl touchesEnded:withEvent:] + 458   
    13  UIKit                               0x003003d0 -[UIWindow _sendTouchesForEvent:] + 567  
    14  UIKit                               0x002e1cb4 -[UIApplication sendEvent:] + 447  
    15  UIKit                               0x002e69bf _UIApplicationHandleEvent + 7672  
    16  GraphicsServices                    0x02d8a822 PurpleEventCallback + 1550  
    17  CoreFoundation                      0x0250fff4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52  
    18  CoreFoundation                      0x02470807 __CFRunLoopDoSource1 + 215  
    19  CoreFoundation                      0x0246da93 __CFRunLoopRun + 979  
    20  CoreFoundation                      0x0246d350 CFRunLoopRunSpecific + 208  
    21  CoreFoundation                      0x0246d271 CFRunLoopRunInMode + 97  
    22  GraphicsServices                    0x02d8900c GSEventRunModal + 217  
    23  GraphicsServices                    0x02d890d1 GSEventRun + 115  
    24  UIKit                  开发者_如何学C             0x002eaaf2 UIApplicationMain + 1160  
    25  MasterApp                           0x00001dbc main + 102  
    26  MasterApp                           0x00001d4d start + 53  
)  
terminate called after throwing an instance of 'NSException'  
Program received signal:  “SIGABRT”.

Thank you in advance

---

You need to set up the parser based on the format of the data you recieve. To get started, Look at the NSXMLParser documentation and the NSXMLParserDelegate documentation. From those pages you can find helpful sample code, SeismicXML and LazyTableImages.