NSUnknownKeyException – this class is not key value coding-compliant for the key

NSUnknownKeyException – this class is not key value coding-compliant for the key common error that most of the Swift beginners would face during the learning period.

Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[<Handbook.StudentEntryController 0x78f948a0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key nametxt.’
*** First throw call stack:
(
0 CoreFoundation 0x02316a14 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x01751e02 objc_exception_throw + 50
2 CoreFoundation 0x02316631 -[NSException raise] + 17
3 Foundation 0x013e71bc -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
4 Foundation 0x0134183a _NSSetUsingKeyValueSetter + 115
5 Foundation 0x013417bf -[NSObject(NSKeyValueCoding) setValue:forKey:] + 295
6 UIKit 0x02cac06d -[UIViewController setValue:forKey:] + 85
7 Foundation 0x0137601d -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 384
8 UIKit 0x02f1fcb4 -[UIRuntimeOutletConnection connect] + 132
9 libobjc.A.dylib 0x0176600c -[NSObject performSelector:] + 62
10 CoreFoundation 0x02246f51 -[NSArray makeObjectsPerformSelector:] + 273
11 UIKit 0x02f1e34e -[UINib instantiateWithOwner:options:] + 2102
12 UIKit 0x02cb3abc -[UIViewController _loadViewFromNibNamed:bundle:] + 429
13 UIKit 0x02cb44f4 -[UIViewController loadView] + 189
14 UIKit 0x02f47b66 -[UITableViewController loadView] + 88
15 UIKit 0x02cb4900 -[UIViewController loadViewIfRequired] + 154
16 UIKit 0x02cbb406 -[UIViewController __viewWillAppear:] + 114
17 UIKit 0x02cde5b9 -[UIViewController(UIContainerViewControllerProtectedMethods) beginAppearanceTransition:animated:] + 202
18 UIKit 0x02cf09cc -[UINavigationController _startCustomTransition:] + 1389
19 UIKit 0x02d02769 -[UINavigationController _startDeferredTransitionIfNeeded:] + 803
20 UIKit 0x02d03ada -[UINavigationController __viewWillLayoutSubviews] + 68
21 UIKit 0x02edfc4a -[UILayoutContainerView layoutSubviews] + 252
22 UIKit 0x02bb5008 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 810
23 libobjc.A.dylib 0x01766059 -[NSObject performSelector:withObject:] + 70
24 QuartzCore 0x029b480a -[CALayer layoutSublayers] + 144
25 QuartzCore 0x029a84ee _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 388
26 QuartzCore 0x029a8352 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
27 QuartzCore 0x0299ae8b _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 317
28 QuartzCore 0x029cee03 _ZN2CA11Transaction6commitEv + 561
29 QuartzCore 0x029d0674 _ZN2CA11Transaction17flush_transactionEv + 50
30 UIKit 0x02ae28bc _UIApplicationHandleEventQueue + 8398
31 CoreFoundation 0x022306ff __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
32 CoreFoundation 0x0222638b __CFRunLoopDoSources0 + 523
33 CoreFoundation 0x022257a8 __CFRunLoopRun + 1032
34 CoreFoundation 0x022250e6 CFRunLoopRunSpecific + 470
35 CoreFoundation 0x02224efb CFRunLoopRunInMode + 123
36 GraphicsServices 0x05cf5664 GSEventRunModal + 192
37 GraphicsServices 0x05cf54a1 GSEventRun + 104
38 UIKit 0x02ae8bfa UIApplicationMain + 160
39 Handbook 0x0007513d main + 93
40 libdyld.dylib 0x04b11a21 start + 1
41 ??? 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

This issue occurs when a storyboard refers to a deleted or renamed IBOutlet. If you navigate to the connection instepctor of the ViewController, you shoud notice an exclaimation mark as shown below.

Remove the IBOutlet mapping by clicking on X mark and remove the orphaned IBOutlet.