iOS Unknown exception thrown out of the blue [duplicate] - ios

Question

This question already has answers here:
Xcode - How to fix 'NSUnknownKeyException', reason: … this class is not key value coding-compliant for the key X" error?
(79 answers)
Closed 7 years ago.
I've began to program an iOS application, but I ran into a sudden problem. The program worked as intended, I had a single view application, with navigation bar with title Title. When I compiled it, it was okay, but then I decided to "retitle" the title bar to say Hello. And after that I've got an error without a slightest idea what for, cause it worked like a minute before this error and the only change was the title of the title bar.
here is the error
Terminating app due to uncaught exception 'NSUnknownKeyException', reason:
[<MapViewController 0xa964410> setValue:forUndefinedKey:]: this class is not key
value coding-compliant for the key titleText.'
*** First throw call stack:
(
0 CoreFoundation 0x027a51e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x025248e5 objc_exception_throw + 44
2 CoreFoundation 0x02834fe1 -[NSException raise] + 17
3 Foundation 0x021e4d9e -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
4 Foundation 0x021511d7 _NSSetUsingKeyValueSetter + 88
5 Foundation 0x02150731 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 267
6 Foundation 0x021b2b0a -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 412
7 UIKit 0x0149b1f4 -[UIRuntimeOutletConnection connect] + 106
8 libobjc.A.dylib 0x025367de -[NSObject performSelector:] + 62
9 CoreFoundation 0x027a076a -[NSArray makeObjectsPerformSelector:] + 314
10 UIKit 0x01499d4d -[UINib instantiateWithOwner:options:] + 1417
11 UIKit 0x013026f5 -[UIViewController _loadViewFromNibNamed:bundle:] + 280
12 UIKit 0x01302e9d -[UIViewController loadView] + 302
13 UIKit 0x013030d3 -[UIViewController loadViewIfRequired] + 78
14 UIKit 0x013035d9 -[UIViewController view] + 35
15 UIKit 0x01223267 -[UIWindow addRootViewControllerViewIfPossible] + 66
16 UIKit 0x012235ef -[UIWindow _setHidden:forced:] + 312
17 UIKit 0x0122386b -[UIWindow _orderFrontWithoutMakingKey] + 49
18 UIKit 0x0122e3c8 -[UIWindow makeKeyAndVisible] + 65
19 Anchor-It 0x00005a39 -[AppDelegate application:didFinishLaunchingWithOptions:] + 585
20 UIKit 0x011de14f -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 309
21 UIKit 0x011deaa1 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1810
22 UIKit 0x011e3667 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
23 UIKit 0x011f7f92 -[UIApplication handleEvent:withNewEvent:] + 3517
24 UIKit 0x011f8555 -[UIApplication sendEvent:] + 85
25 UIKit 0x011e5250 _UIApplicationHandleEvent + 683
26 GraphicsServices 0x0381df02 _PurpleEventCallback + 776
27 GraphicsServices 0x0381da0d PurpleEventCallback + 46
28 CoreFoundation 0x02720ca5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
29 CoreFoundation 0x027209db __CFRunLoopDoSource1 + 523
30 CoreFoundation 0x0274b68c __CFRunLoopRun + 2156
31 CoreFoundation 0x0274a9d3 CFRunLoopRunSpecific + 467
32 CoreFoundation 0x0274a7eb CFRunLoopRunInMode + 123
33 UIKit 0x011e2d9c -[UIApplication _run] + 840
34 UIKit 0x011e4f9b UIApplicationMain + 1225
35 Anchor-It 0x00005dbd main + 141
36 libdyld.dylib 0x03f5e701 start + 1
37 ??? 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

Look at this part of the stack trace:
3 Foundation 0x021e4d9e -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
4 Foundation 0x021511d7 _NSSetUsingKeyValueSetter + 88
5 Foundation 0x02150731 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 267
6 Foundation 0x021b2b0a -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 412
7 UIKit 0x0149b1f4 -[UIRuntimeOutletConnection connect] + 106
You've got a bad connection in your .xib or storyboard file. The view loading process is trying to connect something to some outlet that doesn't exist, resulting in an exception being thrown. Further information about exactly what connection is bad comes from the exception itself:
[<MapViewController 0xa964410> setValue:forUndefinedKey:]: this class is not key
value coding-compliant for the key titleText.'
So, you've got an instance of MapViewController, and UIRuntimeOutletConnection (part of the view loading system) is trying to set an outlet called titleText. MapViewController apparently doesn't have a titleText property. This could happen because you used to have such a property but deleted it, or because you changed the class of the view controller from something else (that had such a property) to MapViewController (which doesn't), etc.