미래를 꿈꾸고 성공을 희망하며

this class is not key value coding-compliant for the key btnSize

책 예제를 따라하거나, 이미 만들어진 ViewController와 mainstory.swift를 합칠 경우,

내부 Widget에 정의한 action에 대해 연결이 깨진 경우가 발생한다.

확인하려면, Xcode에서 Triggered Segues에 링크가 깨져서 노란색으로 경고를 띄워주는 것을 발견할 수 있다. 이것을 다시 만들어서 정의해 주면 된다. 

오류 내용은 아래와 같이 나타난다. 

*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UIViewController 0x103a17520> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key btnSize.'
*** First throw call stack:
(
	0   CoreFoundation                      0x00000001804b910c __exceptionPreprocess + 172
	1   libobjc.A.dylib                     0x0000000180092da8 objc_exception_throw + 72
	2   CoreFoundation                      0x00000001804b8ca0 -[NSException init] + 0
	3   Foundation                          0x0000000180e9da3c -[NSObject(NSKeyValueCoding) setValue:forKey:] + 268
	4   UIKitCore                           0x00000001853b7dc4 -[UIViewController setValue:forKey:] + 76
	5   UIKitCore                           0x00000001857435ec -[UIRuntimeOutletConnection connect] + 80
	6   CoreFoundation                      0x00000001804a5cf0 -[NSArray makeObjectsPerformSelector:] + 192
	7   UIKitCore                           0x0000000185736ee4 -[UINib instantiateWithOwner:options:] + 1420
    8   UIKitCore                           0x00000001853bf7a8 -[UIViewController loadView] + 392
	9   UIKitCore                           0x00000001853bfa64 -[UIViewController loadViewIfRequired] + 152
	10  UIKitCore                           0x00000001853c0000 -[UIViewController view] + 20
	11  UIKitCore                           0x00000001852f4628 -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 912
	12  UIKitCore                           0x00000001852eef70 -[UITabBarController _setSelectedViewController:performUpdates:] + 352
	13  UIKitCore                           0x00000001852eedd4 -[UITabBarController setSelectedViewController:] + 80
	14  UIKitCore                           0x00000001852f3a98 -[UITabBarController _setSelectedViewControllerAndNotify:] + 216
	15  UIKitCore                           0x00000001852f3964 -[UITabBarController _tabBarItemClicked:] + 160
	16  UIKitCore                           0x0000000185b36e3c -[UIApplication sendAction:to:from:forEvent:] + 96
	17  UIKitCore                           0x00000001850f969c -[UITabBar _sendAction:withEvent:] + 380
	18  UIKitCore                           0x0000000185b36e3c -[UIApplication sendAction:to:from:forEvent:] + 96
	19  UIKitCore                           0x000000018540c830 -[UIControl sendAction:to:forEvent:] + 108
	20  UIKitCore                           0x000000018540cb74 -[UIControl _sendActionsForEvents:withEvent:] + 268
	21  UIKitCore                           0x00000001850fbfb0 -[UITabBar _buttonUp:] + 96
	22  UIKitCore                           0x0000000185b36e3c -[UIApplication sendAction:to:from:forEvent:] + 96
	23  UIKitCore                           0x000000018540c830 -[UIControl sendAction:to:forEvent:] + 108
	24  UIKitCore                           0x000000018540cb74 -[UIControl _sendActionsForEvents:withEvent:] + 268
	25  UIKitCore                           0x000000018540b80c -[UIControl touchesEnded:withEvent:] + 392
	26  UIKitCore                           0x0000000185b6aa10 -[UIWindow _sendTouchesForEvent:] + 972
	27  UIKitCore                           0x0000000185b6be20 -[UIWindow sendEvent:] + 2840
	28  UIKitCore                           0x0000000185b4b80c -[UIApplication sendEvent:] + 376
	29  UIKitCore                           0x0000000185bd5c70 __dispatchPreprocessedEventFromEventQueue + 1156
	30  UIKitCore                           0x0000000185bd8c00 __processEventQueue + 5592
	31  UIKitCore                           0x0000000185bd0f10 updateCycleEntry + 156
	32  UIKitCore                           0x00000001850a5cec _UIUpdateSequenceRun + 76
	33  UIKitCore                           0x0000000185a60858 schedulerStepScheduledMainSection + 168
	34  UIKitCore                           0x0000000185a5fc90 runloopSourceCallback + 80
	35  CoreFoundation                      0x000000018041d294 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
	36  CoreFoundation                      0x000000018041d1dc __CFRunLoopDoSource0 + 172
	37  CoreFoundation                      0x000000018041c940 __CFRunLoopDoSources0 + 232
	38  CoreFoundation                      0x0000000180416e84 __CFRunLoopRun + 788
	39  CoreFoundation                      0x00000001804166f4 CFRunLoopRunSpecific + 552
	40  GraphicsServices                    0x00000001905e5b10 GSEventRunModal + 160
	41  UIKitCore                           0x0000000185b319dc -[UIApplication _run] + 796
	42  UIKitCore                           0x0000000185b35bd4 UIApplicationMain + 124
	43  UIKitCore                           0x0000000184f0a334 block_destroy_helper.22 + 9660
	44  Tab.debug.dylib                     0x0000000102f0103c $sSo21UIApplicationDelegateP5UIKitE4mainyyFZ + 120
	45  Tab.debug.dylib                     0x0000000102f00fb4 $s3Tab11AppDelegateC5$mainyyFZ + 44
	46  Tab.debug.dylib                     0x0000000102f010b8 __debug_main_executable_dylib_entry_point + 28
	47  dyld                                0x0000000102479410 start_sim + 20
	48  ???                                 0x00000001025ca154 0x0 + 4334592340
	49  ???                                 0x9874000000000000 0x0 + 10985405391063482368
)
libc++abi: terminating due to uncaught exception of type NSException

Exception	NSException *	
"[<UIViewController 0x103a17520> setValue:forUndefinedKey:]: 
this class is not key value coding-compliant for the key btnSize."	0x0000600000c9dfe0

익명함수(클로져, Closure) 이해하기

위의 방식을 이용한 아래의 예제를 보시면서 이해해보세요.

위와 같이 실행구문은 변함이 없으나, 함수 호출을 정의하는 부분이 많이 축약(함수명, 파라미터의 자료형 등) 됩니다.

사실 클로져에 대한 활용은 많은 예시문을 별도로 보관하고 계시다가 발췌해서 이용하거나, 기존 것을 활용해서 수정해서 사용하시면서 익히시는 것이 많은 도움이 될 것입니다. 특히, 집합 관련하여 filter 등을 활용한 예제들은 소스코드를 많이 간결하게 만들어주기 때문에 꼭 한번 찾아 보세요.