numberOfRowsInSection - unrecognized selector sent to instance issue

Question

I keep getting this issue while trying to run my application. It compiles successfully:

    GNU gdb 6.3.50-20050815 (Apple version gdb-1518) (Thu Jan 27 08:30:35 UTC 2011)
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This GDB was configured as "i386-apple-darwin".Attaching to process 1833.
2011-06-01 10:20:07.576 MicroBetas[1833:207] -[UIApplication tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x4d0f9e0
2011-06-01 10:20:07.580 MicroBetas[1833:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIApplication tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x4d0f9e0'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00ecbbe9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x00cc05c2 objc_exception_throw + 47
    2   CoreFoundation                      0x00ecd6fb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
    3   CoreFoundation                      0x00e3d366 ___forwarding___ + 966
    4   CoreFoundation                      0x00e3cf22 _CF_forwarding_prep_0 + 50
    5   UIKit                               0x001cff16 -[UISectionRowData refreshWithSection:tableView:tableViewRowData:] + 1834
    6   UIKit                               0x001cd9e7 -[UITableViewRowData numberOfRows] + 108
    7   UIKit                               0x000848c2 -[UITableView noteNumberOfRowsChanged] + 132
    8   UIKit                               0x000912b8 -[UITableView reloadData] + 773
    9   UIKit                               0x0008e470 -[UITableView layoutSubviews] + 42
    10  QuartzCore                          0x01612451 -[CALayer layoutSublayers] + 181
    11  QuartzCore                          0x0161217c CALayerLayoutIfNeeded + 220
    12  QuartzCore                          0x0160b37c _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 310
    13  QuartzCore                          0x0160b0d0 _ZN2CA11Transaction6commitEv + 292
    14  UIKit                               0x0001a19f -[UIApplication _reportAppLaunchFinished] + 39
    15  UIKit                               0x0001a659 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 690
    16  UIKit                               0x00024db2 -[UIApplication handleEvent:withNewEvent:] + 1533
    17  UIKit                               0x0001d202 -[UIApplication sendEvent:] + 71
    18  UIKit                               0x00022732 _UIApplicationHandleEvent + 7576
    19  GraphicsServices                    0x01021a36 PurpleEventCallback + 1550
    20  CoreFoundation                      0x00ead064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
    21  CoreFoundation                      0x00e0d6f7 __CFRunLoopDoSource1 + 215
    22  CoreFoundation                      0x00e0a983 __CFRunLoopRun + 979
    23  CoreFoundation                      0x00e0a240 CFRunLoopRunSpecific + 208
    24  CoreFoundation                      0x00e0a161 CFRunLoopRunInMode + 97
    25  UIKit                               0x00019fa8 -[UIApplication _run] + 636
    26  UIKit                               0x0002642e UIApplicationMain + 1160
    27  MicroBetas                          0x00002299 main + 121
    28  MicroBetas                          0x00002215 start + 53
)
terminate called after throwing an instance of 'NSException'
sharedlibrary apply-load-rules all
Current language:  auto; currently objective-c
(gdb) 

Code it appears to be getting stuck at:

- (NSInteger)tableView:(UITableView *)tableView 
 numberOfRowsInSection:(NSInteger)section {
    return [self.colorNames count];
}

Answer 1

The class instance, which you have assign to DataSource doesn't implement the UITableViewDataSource functions.

 @interface MyClassController :UIViewController <UITableViewDelegate,UITableViewDataSource>

try like below.

myTableView.dataSource = self;

*Note self is the instance of MyClassController

implement the method of UITableViewDataSource protocol.

Answer 2

It's highly likely that you intended your application delegate to be your data source but accidentally made the File's Owner, which is the UIApplication object, the datasource. This is the reason the application object seems to be getting the data requests.

Answer 3

Check your data source and delegate outlet are properly connected to your viewController... This worked for me..

Answer 4

The problem is most likely caused by assigning the File's Owner as the Table View's delegate and data source. As others have mentioned, the File's Owner is a UIApplication object which does not conform to the UITableViewDelegate and UITableViewDataSource protocols that the UITableView must conform to. If you are using IB, simply connect the Table View to it's respected View Controller for both the delegate and data source instead of the File's Owner.