Swift: App terminating due to uncaught exception 'NSUnknownKeyException'

Question

I'm developing a simple game and I am having trouble when a particular UIViewController (called SPSwipes.swift) is loaded. On the screen, there are three buttons: 5, 10, and 25. When one is picked, a variable is set in that scene and the player moves on to the main Game: GameScene.swift.

As far as I am aware, the variables are recognised in the GameScene, but there is a 'NSUnknownKeyException' error when I open up the SPSwipes view in the simulator. This is done by way of a segue. Here is the error in more detail:

2014-11-09 15:32:43.718 Swipe Racer[2644:1620056] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<Swipe_Racer.SPSwipes 0x7fbf52d461b0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key fiveSwipes.'
*** First throw call stack:
(
0   CoreFoundation                      0x000000010c021f35 __exceptionPreprocess + 165
1   libobjc.A.dylib                     0x000000010dd1bbb7 objc_exception_throw + 45
2   CoreFoundation                      0x000000010c021b79 -[NSException raise] + 9
3   Foundation                          0x000000010c4397b3 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 259
4   CoreFoundation                      0x000000010bf6be80 -[NSArray makeObjectsPerformSelector:] + 224
5   UIKit                               0x000000010cd28c7d -[UINib instantiateWithOwner:options:] + 1506
6   UIKit                               0x000000010cb87f98 -[UIViewController _loadViewFromNibNamed:bundle:] + 242
7   UIKit                               0x000000010cb88588 -[UIViewController loadView] + 109
8   UIKit                               0x000000010cb887f9 -[UIViewController loadViewIfRequired] + 75
9   UIKit                               0x000000010cb88c8e -[UIViewController view] + 27
10  UIKit                               0x000000010caa7ca9 -[UIWindow addRootViewControllerViewIfPossible] + 58
11  UIKit                               0x000000010caa8041 -[UIWindow _setHidden:forced:] + 247
12  UIKit                               0x000000010cab472c -[UIWindow makeKeyAndVisible] + 42
13  UIKit                               0x000000010ca5f061 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2628
14  UIKit                               0x000000010ca61d2c -[UIApplication _runWithMainScene:transitionContext:completion:] + 1350
15  UIKit                               0x000000010ca60bf2 -[UIApplication workspaceDidEndTransaction:] + 179
16  FrontBoardServices                  0x000000011383b2a3 __31-[FBSSerialQueue performAsync:]_block_invoke + 16
17  CoreFoundation                      0x000000010bf5753c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
18  CoreFoundation                      0x000000010bf4d285 __CFRunLoopDoBlocks + 341
19  CoreFoundation                      0x000000010bf4d045 __CFRunLoopRun + 2389
20  CoreFoundation                      0x000000010bf4c486 CFRunLoopRunSpecific + 470
21  UIKit                               0x000000010ca60669 -[UIApplication _run] + 413
22  UIKit                               0x000000010ca63420 UIApplicationMain + 1282
23  Swipe Racer                         0x000000010be380de top_level_code + 78
24  Swipe Racer                         0x000000010be3811a main + 42
25  libdyld.dylib                       0x000000010e507145 start + 1
26  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

As you can see, there is an issue with my first variable, fiveSwipes (and I would imagine that there would be errors with the two others). What does 'this class is not key value coding-compliant for the key fiveSwipes' mean? How should I go about fixing it?

My SPSwipes.swift file:

class SPSwipes: UIViewController {

var no_of_swipes = 0

@IBAction func fiveSwipes(sender: AnyObject) {
    no_of_swipes = 5

//and so on

}

Thank you in advance,

Will

Answer 1

The problem was that the button was linked to numerous IBActions - three of which didn't exist. I right clicked on the button in the Interface Builder and removed the old and irrelevant links, fixing the problem.