unrecognized selector sent to instance of custom class - objective-c

Question

Here is class header:
#interface ChallengeItem : NSObject
.......
- (NSString *) getAlertIntervalInString;
- (void) createReminder;
#end
some implementation in .m file:
- (NSString *) getAlertIntervalInString {
... do something
}
- (void)createReminder {
... do something
}
I call
for (int i = 0; i < [self count]; i++) {
ChallengeItem *currentItem = [self getChallengeAtIndex:i];
if (currentItem.isStarted) {
[currentItem createReminder];
}
}
and receive an unrecognized selector error, but when I change
[currentItem createReminder];
to
[currentItem getAlertIntervalInString];
error isn't appear.
What is the problem?
Here is the console log
Current language: auto; currently objective-c 2011-11-23 00:56:40.056
30 Day Challenge[379:12b03] -[ChallengeItem createReminder]:
unrecognized selector sent to instance 0x6079900 2011-11-23
00:56:40.147 30 Day Challenge[379:12b03] * Terminating app due to
uncaught exception 'NSInvalidArgumentException', reason:
'-[ChallengeItem createReminder]: unrecognized selector sent to
instance 0x6079900'
* Call stack at first throw:
(
0 CoreFoundation 0x00fb35a9 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x01107313 objc_exception_throw + 44
2 CoreFoundation 0x00fb50bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3 CoreFoundation 0x00f24966 ___forwarding___ + 966
4 CoreFoundation 0x00f24522 _CF_forwarding_prep_0 + 50
5 30 Day Challenge 0x00006950 -[ChallengeCollection setRemindersForStartedChallenges] + 144
6 30 Day Challenge 0x00002f27 -[_0_Day_ChallengeAppDelegate applicationDidEnterBackground:] + 151
7 UIKit 0x00209a40 -[UIApplication _handleApplicationSuspend:eventInfo:] + 607
8 UIKit 0x00213039 -[UIApplication handleEvent:withNewEvent:] + 4127
9 UIKit 0x0020aabf -[UIApplication sendEvent:] + 71
10 UIKit 0x0020ff2e _UIApplicationHandleEvent + 7576
11 GraphicsServices 0x01712992 PurpleEventCallback + 1550
12 CoreFoundation 0x00f94944 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
13 CoreFoundation 0x00ef4cf7 __CFRunLoopDoSource1 + 215
14 CoreFoundation 0x00ef1f83 __CFRunLoopRun + 979
15 CoreFoundation 0x00ef1840 CFRunLoopRunSpecific + 208
16 CoreFoundation 0x00ef1761 CFRunLoopRunInMode + 97
17 GraphicsServices 0x017111c4 GSEventRunModal + 217
18 GraphicsServices 0x01711289 GSEventRun + 115
19 UIKit 0x00213c93 UIApplicationMain + 1160
20 30 Day Challenge 0x00002059 main + 121
21 30 Day Challenge 0x00001fd5 start + 53
22 ??? 0x00000001 0x0 + 1
)
terminate called throwing an exception(gdb)

Answer 1

I don't see any obvious problems with your code. To make sure getChallengeAtIndex is in fact returning ChallengeItem instances, you could put a breakpoint at that line and inspect the returned values.

Answer 2

After you install the new version of XCode, the problem will be gone.