我刚从Apple收到了这些报告，但我无法弄清楚我的ViewController上的哪个属性丢失或未在IB中正确连接。事实上，我已经彻底检查了它们，并且在编译项目时没有得到任何警告，这使得我没有其他选择来重新编写所有内容。
Last Exception Backtrace:
0 CoreFoundation 0x182b92950 __exceptionPreprocess + 132
1 libobjc.A.dylib 0x18f56c1fc objc_exception_throw + 60
2 CoreFoundation 0x182b925d4 -[NSException raise] + 12
3 Foundation 0x183650720 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 256
4 CoreFoundation 0x182ade09c -[NSArray makeObjectsPerformSelector:] + 248
5 UIKit 0x185f16dd0 -[UINib instantiateWithOwner:options:] + 1232
6 UIKit 0x185e5b878 -[UIViewController _loadViewFromNibNamed:bundle:] + 280
7 UIKit 0x185b5c488 -[UIViewController loadViewIfRequired] + 88
8 UIKit 0x185b5c3f4 -[UIViewController view] + 32
9 UIKit 0x185d09868 -[UINavigationController _startCustomTransition:] + 704
10 UIKit 0x185c13f54 -[UINavigationController _startDeferredTransitionIfNeeded:] + 464
11 UIKit 0x185c13d24 -[UINavigationController __viewWillLayoutSubviews] + 56
12 UIKit 0x185c13ca4 -[UILayoutContainerView layoutSubviews] + 200
13 UIKit 0x185b56ff8 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 348
14 QuartzCore 0x185748258 -[CALayer layoutSublayers] + 184
15 QuartzCore 0x185742e20 CA::Layer::layout_if_needed(CA::Transaction*) + 300
16 QuartzCore 0x185742cd8 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 32
17 QuartzCore 0x185742560 CA::Context::commit_transaction(CA::Transaction*) + 280
18 QuartzCore 0x185742304 CA::Transaction::commit() + 424
19 QuartzCore 0x18573bc38 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 80
20 CoreFoundation 0x182b530a8 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
21 CoreFoundation 0x182b50330 __CFRunLoopDoObservers + 372
22 CoreFoundation 0x182b506bc __CFRunLoopRun + 764
23 CoreFoundation 0x182a916d0 CFRunLoopRunSpecific + 452
24 GraphicsServices 0x18872dc0c GSEventRunModal + 168
25 UIKit 0x185bc2fdc UIApplicationMain + 1156
26 AppName 0x10012e1f4 main (main.m:22)
27 libdyld.dylib 0x18fb5faa0 start + 4