xcode - 尝试构建基于简单 UITabBarController 的 iOS 应用程序时出现运行时错误

Question

我的代码可以编译，但当我尝试启动它时遇到运行时错误。

这是运行时错误:

2011-04-25 23:56:40.689 Noun[39033:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<NounAppDelegate 0x4e1c400> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key viewController.'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00dc75a9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x00f1b313 objc_exception_throw + 44
    2   CoreFoundation                      0x00dc74e1 -[NSException raise] + 17
    3   Foundation                          0x0002f677 _NSSetUsingKeyValueSetter + 135
    4   Foundation                          0x0002f5e5 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 285
    5   UIKit                               0x004b330c -[UIRuntimeOutletConnection connect] + 112
    6   CoreFoundation                      0x00d3d8cf -[NSArray makeObjectsPerformSelector:] + 239
    7   UIKit                               0x004b1d23 -[UINib instantiateWithOwner:options:] + 1041
    8   UIKit                               0x004b3ab7 -[NSBundle(UINSBundleAdditions) loadNibNamed:owner:options:] + 168
    9   UIKit                               0x002b917a -[UIApplication _loadMainNibFile] + 172
    10  UIKit                               0x002b9cf4 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 291
    11  UIKit                               0x002c4617 -[UIApplication handleEvent:withNewEvent:] + 1533
    12  UIKit                               0x002bcabf -[UIApplication sendEvent:] + 71
    13  UIKit                               0x002c1f2e _UIApplicationHandleEvent + 7576
    14  GraphicsServices                    0x0171f992 PurpleEventCallback + 1550
    15  CoreFoundation                      0x00da8944 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
    16  CoreFoundation                      0x00d08cf7 __CFRunLoopDoSource1 + 215
    17  CoreFoundation                      0x00d05f83 __CFRunLoopRun + 979
    18  CoreFoundation                      0x00d05840 CFRunLoopRunSpecific + 208
    19  CoreFoundation                      0x00d05761 CFRunLoopRunInMode + 97
    20  UIKit                               0x002b97d2 -[UIApplication _run] + 623
    21  UIKit                               0x002c5c93 UIApplicationMain + 1160
    22  Noun                                0x00001e68 main + 102
    23  Noun                                0x00001df9 start + 53
)
terminate called after throwing an instance of 'NSException'

这是我的代码(相关方法)

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    //Initiate TabBarController
    self.tabBarController = [[UITabBarController alloc] init];

    NSMutableArray *viewControllersForTabController = [[NSMutableArray alloc] initWithCapacity:2];

    NounViewController *firstViewController = [[NounViewController alloc] initWithNibName:@"NounViewController" bundle:[NSBundle mainBundle]];
    [viewControllersForTabController addObject:firstViewController];
    [firstViewController release];

    PostLoginViewController *secondViewController = [[PostLoginViewController alloc] initWithNibName:@"PostLoginViewController" bundle:[NSBundle mainBundle]];
    [viewControllersForTabController addObject:secondViewController];
    [secondViewController release];

    [tabBarController setViewControllers:viewControllersForTabController];
    [viewControllersForTabController release];

    [window addSubview:tabBarController.view];

    return YES;
}

我确信这可能是我忘记做的一些微不足道的事情，我正在慢慢跟上 iOS 开发的速度

Answer 1

“NSUnknownKeyException”当您访问不存在的 key 时会出现此异常，这并不总是因为代码，Interface Builder 中可能存在一些错误连接。上面的代码没有问题，我试了一下，运行成功。尝试检查您的界面生成器连接，可能您缺少一些东西。最有可能的是，您首先尝试通过 IB 添加 tabBarController，然后通过代码执行此操作。