Objective-C NSInvalidArgumentException

Question

I have a segemented control with three choices, each choice does a different calculations. The calculations are doing manipulating strings.

I notice that when I first start the app, the strings are nil, btw. If I touch all three options on the segmented control, the app will crash, and here is the stack trace.

I've searched everywhere but can't find the problem still.

[Session started at 2011-02-25 01:21:03 -0500.]
2011-02-25 01:21:07.075 tipApp[2184:207] -[_UIStretchableImage isEqualToString:]: unrecognized selector sent to instance 0x4b5c0a0
2011-02-25 01:21:07.078 tipApp[2184:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[_UIStretchableImage isEqualToString:]: unrecognized selector sent to instance 0x4b5c0a0'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00db7be9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x00f0c5c2 objc_exception_throw + 47
    2   CoreFoundation                      0x00db96fb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
    3   CoreFoundation                      0x00d29366 ___forwarding___ + 966
    4   CoreFoundation                      0x00d28f22 _CF_forwarding_prep_0 + 50
    5   tipApp                              0x00006f13 -[tipAppViewController exact] + 56
    6   tipApp                              0x00006ed3 -[tipAppViewController mirror] + 4772
    7   tipApp                              0x000057f2 -[tipAppViewController segmentedControlIndexChanged] + 104
    8   UIKit                               0x002c0a6e -[UIApplication sendAction:to:from:forEvent:] + 119
    9   UIKit                               0x0034f1b5 -[UIControl sendAction:to:forEvent:] + 67
    10  UIKit                               0x00351647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
    11  UIKit                               0x0034f16c -[UIControl sendActionsForControlEvents:] + 49
    12  UIKit                               0x0038e6b2 -[UISegmentedControl setSelectedSegmentIndex:] + 574
    13  UIKit                               0x0039317e -[UISegmentedControl touchesBegan:withEvent:] + 971
    14  UIKit                               0x002e5025 -[UIWindow _sendTouchesForEvent:] + 395
    15  UIKit                               0x002c637a -[UIApplication sendEvent:] + 447
    16  UIKit                               0x002cb732 _UIApplicationHandleEvent + 7576
    17  GraphicsServices                    0x016eda36 PurpleEventCallback + 1550
    18  CoreFoundation                      0x00d99064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
    19  CoreFoundation                      0x00cf96f7 __CFRunLoopDoSource1 + 215
    20  CoreFoundation                      0x00cf6983 __CFRunLoopRun + 979
    21  CoreFoundation                      0x00cf6240 CFRunLoopRunSpecific + 208
    22  CoreFoundation                      0x00cf6161 CFRunLoopRunInMode + 97
    23  GraphicsServices                    0x016ec268 GSEventRunModal + 217
    24  GraphicsServices                    0x016ec32d GSEventRun + 115
    25  UIKit                               0x002cf42e UIApplicationMain + 1160
    26  tipApp                              0x00002888 main + 102
    27  tipApp                              0x00002819 start + 53
)
terminate called after throwing an instance of 'NSException'

[Session started at 2011-02-25 01:26:59 -0500.]

Answer 1

Can you post the code for the segmented control? Are you trying to go through the subviews on a UIScrollview? That may cause the exception to thrown. Check out:

http://wiresareobsolete.com/wordpress/2010/03/uiscrollview-has-a-secret/

Answer 2

It looks like in your -[tipAppViewController exact] method you are sending the isEqualToString: selector to an object that does not handle it.

If that's not helpful, maybe post the code for the exact method.