我是编程的初学者，也是Stack Overflow的新手。我仍在弄清代码和该网站的工作方式，所以如果无法正确使用它们，我感到抱歉。 (我不是英语母语人士，但我会尽力解释我的问题)
我正在使用Xcode版本8.1和Swift。
我正在为我的学校项目构建一个应用程序。我已经创建了待办事项应用和倒数计时器应用。因此，我现在想将它们放到一个应用程序中。
我创建了一个新项目并插入了Tab Bar Controller。然后复制待办事项和倒数计时器应用程序中使用的所有文件，并设置情节提要。
没有警告标记，但是当我运行模拟器时，出现错误并且模拟器停止。我得到的错误是AppDelegate.swift中此行中的“线程1:信号SIGABRT”:
class AppDelegate: UIResponder, UIApplicationDelegate {
控制台中的消息是:
2017-01-06 20:32:22.207 PP Final App[61701:3259153] Unknown class PomodoroViewController in Interface Builder file.
2017-01-06 20:32:22.713 PP Final App[61701:3259153] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UIViewController 0x7fd7faf075d0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key lbTimer.'
*** First throw call stack:
(
0 CoreFoundation 0x00000001100c234b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x000000010fb2321e objc_exception_throw + 48
2 CoreFoundation 0x00000001100c2299 -[NSException raise] + 9
3 Foundation 0x000000010f63326f -[NSObject(NSKeyValueCoding) setValue:forKey:] + 291
4 UIKit 0x000000011067f4ef -[UIViewController setValue:forKey:] + 88
5 UIKit 0x00000001108f379e -[UIRuntimeOutletConnection connect] + 109
6 CoreFoundation 0x0000000110067590 -[NSArray makeObjectsPerformSelector:] + 256
7 UIKit 0x00000001108f2122 -[UINib instantiateWithOwner:options:] + 1867
8 UIKit 0x0000000110685c21 -[UIViewController _loadViewFromNibNamed:bundle:] + 386
9 UIKit 0x0000000110686543 -[UIViewController loadView] + 177
10 UIKit 0x0000000110686878 -[UIViewController loadViewIfRequired] + 201
11 UIKit 0x00000001106870cc -[UIViewController view] + 27
12 UIKit 0x00000001106e52df -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 483
13 UIKit 0x00000001106e4721 -[UITabBarController transitionFromViewController:toViewController:] + 59
14 UIKit 0x00000001106e05e2 -[UITabBarController _setSelectedViewController:] + 365
15 UIKit 0x00000001106e0464 -[UITabBarController setSelectedViewController:] + 234
16 UIKit 0x000000011059e6e6 +[UIView(Animation) performWithoutAnimation:] + 90
17 UIKit 0x00000001106daa00 -[UITabBarController _selectDefaultViewControllerIfNecessaryWithAppearanceTransitions:] + 354
18 UIKit 0x00000001106dbb7a -[UITabBarController viewWillAppear:] + 206
19 UIKit 0x000000011068ca0f -[UIViewController _setViewAppearState:isAnimating:] + 692
20 UIKit 0x000000011068d11f -[UIViewController __viewWillAppear:] + 147
21 UIKit 0x000000011068e913 -[UIViewController viewWillMoveToWindow:] + 507
22 UIKit 0x0000000110595151 -[UIView(Hierarchy) _willMoveToWindow:withAncestorView:] + 621
23 UIKit 0x00000001105a5cf0 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 451
24 UIKit 0x00000001105947a1 -[UIView(Hierarchy) addSubview:] + 838
25 UIKit 0x0000000110550f5b -[UIWindow addRootViewControllerViewIfPossible] + 849
26 UIKit 0x00000001105513a2 -[UIWindow _setHidden:forced:] + 293
27 UIKit 0x0000000110564cb5 -[UIWindow makeKeyAndVisible] + 42
28 UIKit 0x00000001104ddc89 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4818
29 UIKit 0x00000001104e3de9 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1731
30 UIKit 0x00000001104e0f69 -[UIApplication workspaceDidEndTransaction:] + 188
31 FrontBoardServices 0x0000000113ed3723 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
32 FrontBoardServices 0x0000000113ed359c -[FBSSerialQueue _performNext] + 189
33 FrontBoardServices 0x0000000113ed3925 -[FBSSerialQueue _performNextFromRunLoopSource] + 45
34 CoreFoundation 0x0000000110067311 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
35 CoreFoundation 0x000000011004c59c __CFRunLoopDoSources0 + 556
36 CoreFoundation 0x000000011004ba86 __CFRunLoopRun + 918
37 CoreFoundation 0x000000011004b494 CFRunLoopRunSpecific + 420
38 UIKit 0x00000001104df7e6 -[UIApplication _run] + 434
39 UIKit 0x00000001104e5964 UIApplicationMain + 159
40 PP Final App 0x000000010f52c1cf main + 111
41 libdyld.dylib 0x000000011373c68d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
在此消息中，我看到“Interface Builder文件中的未知类PomodoroViewController”。这是问题，对不对？但我不知道为什么收到此消息。文件中有问题吗？
我使用Tab Bar Controller的方式正确吗？
这是Pomodoro View Controller的代码文件:
PomodoroViewController
import UIKit
class PomodoroViewController: UIViewController {
@IBOutlet weak var lbTimer: UILabel!
let pomodoroTime: TimeInterval = 60 * 25 //Pomodoro Timer 25 minutes
let formatter = DateFormatter()
var theTime: TimeInterval = 0.0
override func viewDidLoad(){
super.viewDidLoad()
formatter.dateFormat = "mm:ss"
let startTime = Date(timeIntervalSinceReferenceDate: pomodoroTime)
lbTimer.text = formatter.string(from: startTime)
}
override func didReceiveMemoryWarning(){
super.didReceiveMemoryWarning()
}
@IBAction func countDown(_ sender: UIButton) {
theTime = pomodoroTime
Timer.scheduledTimer(timeInterval: 1.0,
target: self,
selector: #selector(PomodoroViewController.tickTimer(timer:)),
userInfo: nil,
repeats: true)
}
func tickTimer(timer: Timer){
theTime -= 1.0
let newTime = Date(timeIntervalSinceReferenceDate: theTime)
if theTime < 0.1 {
timer.invalidate()
}
}
}
这就是情节提要的样子:
storyboard
最佳答案
该错误的含义是:
PomodoroViewController。但是... PomodoroViewController不存在。 该消息说，iOS试图找到
PomodoroViewController，但是它不存在，因此它尝试使用UIViewController。除了UIViewController没有lbTimer属性之外，这会使应用程序崩溃。发生这种情况的原因有两个:
PomodoroViewController复制到新项目。 在第二种情况下，请确保在Xcode窗口右侧的文件检查器中检查了文件:
关于ios - 为什么是“ unknown class ”？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41513564/