Dynamic Button Problem: unrecognized selector sent to instance

Question

I am dynamically creating buttons on iPhone app.

---

UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

[btn setTitle:atitle forState:UIControlStateNormal];

[btn addTarget:self action:@selector(buttonTouched:) forControlEvents:UIControlEventTouchUpInside]; // handle touch

[buttons addObject:btn];


----------

-(void) buttonTouched:sender{
}

----------

-[NSCFString buttonTouched:]: unrecognized selector sent to instance 0x592ef70
2010-07-28 08:59:43.551 DataManager[1707:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString buttonTouched:]: unrecognized selector sent to instance 0x592ef70'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x02398919 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x024e65de objc_exception_throw + 47
    2   CoreFoundation                      0x0239a42b -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
    3   CoreFoundation                      0x0230a116 ___forwarding___ + 966
    4   CoreFoundation                      0x02309cd2 _CF_forwarding_prep_0 + 50
    5   UIKit                               0x002bce14 -[UIApplication sendAction:to:from:forEvent:] + 119
    6   UIKit                               0x003466c8 -[UIControl sendAction:to:forEvent:] + 67
    7   UIKit                               0x00348b4a -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
    8   UIKit                               0x003476f7 -[UIControl touchesEnded:withEvent:] + 458
    9   UIKit                               0x00534070 _UIGestureRecognizerUpdateObserver + 3687
    10  CoreFoundation                      0x02379d1b __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 27
    11  CoreFoundation                      0x0230e987 __CFRunLoopDoObservers + 295
    12  CoreFoundation                      0x022d7c17 __CFRunLoopRun + 1575
    13  CoreFoundation                      0x022d7280 CFRunLoopRunSpecific + 208
    14  CoreFoundation                      0x022d71a1 CFRunLoopRunInMode + 97
    15  GraphicsServices                    0x02bfd2c8 GSEventRunModal + 217
    16  GraphicsServices                    0x02bfd38d GSEventRun + 115
    17  UIKit                               0x002cab58 UIApplicationMain + 1160
    18  DataManager                         0x00001c4c main + 102
    19  DataManager                         0x00001bdd start + 53
)
terminate called after throwing an instance of 'NSException'
Program received signal:  “SIGABRT”.

Any ideas?

Answer 1

Should be:

-(void)buttonTouched:(id)sender { }

Answer 2

Because you included a colon (:) in your selector argument to addTarget, the receiving selector must accept a parameter. The runtime doesn't recognize the selector @selector(buttonTouched:), because there isn't a method with that name that accepts a parameter. Change the method signature to accept a parameter of type id to resolve this issue.