title: Swift NSUnknownKeyException
body: <p>Started learning Swift a day or two ago. I run into this error more times than I'd like -- essentially, I realize that it has something to do with the IBOutlets. Removing all outlets and buttons/objects in the storyboard, and manually re-adding them seems to do the trick.</p>
  
  <p>In the future if this error occurs, and I'm working on a large project, I would like to know how to diagnose which IBOutlet it is, or whatever it may be that is causing this.</p>
  
  <p>I have a copy of the project on GitHub <a href="https://github.com/mdobrenko/keyboardapptest" rel="noreferrer">here</a> if anyone wants to take a look and leave a few words of advice.</p>
  
  <p>Thanks a ton in advance!</p>
  
  <pre><code>2015-06-04 22:24:31.607 Controlling The Keyboard[1343:16382] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[&lt;Controlling_The_Keyboard.ViewController 0x7f80896418b0&gt; setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key enterButton.'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x0000000104855c65 __exceptionPreprocess + 165
      1   libobjc.A.dylib                     0x00000001063c0bb7 objc_exception_throw + 45
      2   CoreFoundation                      0x00000001048558a9 -[NSException raise] + 9
      3   Foundation                          0x0000000104c73b53 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 259
      4   CoreFoundation                      0x000000010479dd50 -[NSArray makeObjectsPerformSelector:] + 224
      5   UIKit                               0x00000001053cc52b -[UINib instantiateWithOwner:options:] + 1506
      6   UIKit                               0x0000000105224718 -[UIViewController _loadViewFromNibNamed:bundle:] + 242
      7   UIKit                               0x0000000105224d08 -[UIViewController loadView] + 109
      8   UIKit                               0x0000000105224f79 -[UIViewController loadViewIfRequired] + 75
      9   UIKit                               0x000000010522540e -[UIViewController view] + 27
      10  UIKit                               0x00000001051402c9 -[UIWindow addRootViewControllerViewIfPossible] + 58
      11  UIKit                               0x000000010514068f -[UIWindow _setHidden:forced:] + 247
      12  UIKit                               0x000000010514ce21 -[UIWindow makeKeyAndVisible] + 42
      13  UIKit                               0x00000001050f0457 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2732
      14  UIKit                               0x00000001050f31de -[UIApplication _runWithMainScene:transitionContext:completion:] + 1349
      15  UIKit                               0x00000001050f20d5 -[UIApplication workspaceDidEndTransaction:] + 179
      16  FrontBoardServices                  0x0000000107ed05e5 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 21
      17  CoreFoundation                      0x000000010478941c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
      18  CoreFoundation                      0x000000010477f165 __CFRunLoopDoBlocks + 341
      19  CoreFoundation                      0x000000010477ef25 __CFRunLoopRun + 2389
      20  CoreFoundation                      0x000000010477e366 CFRunLoopRunSpecific + 470
      21  UIKit                               0x00000001050f1b42 -[UIApplication _run] + 413
      22  UIKit                               0x00000001050f4900 UIApplicationMain + 1282
      23  Controlling The Keyboard            0x0000000104654f37 main + 135
      24  libdyld.dylib                       0x0000000106b18145 start + 1
  )
  libc++abi.dylib: terminating with uncaught exception of type NSException
  (lldb) 
  </code></pre>