iOS 尝试使用 UIPickerView 加载视图时应用程序崩溃 NSUnknownKeyException

Question

我有一个应用程序 UIPickerView。第二次我尝试打开包含它的视图时，应用程序崩溃并显示 NSUnknownKeyException。

这是日志：

    2015-08-01 17:43:50.572 Patient Consent Project[1748:47245] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<Patient_Consent_Project.ProcedurePicker 0x7ff381d1dd50> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key picker.'
*** First throw call stack:
(
0   CoreFoundation                      0x000000010de51c65 __exceptionPreprocess + 165
1   libobjc.A.dylib                     0x000000010f9bcbb7 objc_exception_throw + 45
2   CoreFoundation                      0x000000010de518a9 -[NSException raise] + 9
3   Foundation                          0x000000010e26fb53 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 259
4   CoreFoundation                      0x000000010dd99d50 -[NSArray makeObjectsPerformSelector:] + 224
5   UIKit                               0x000000010e9c84eb -[UINib instantiateWithOwner:options:] + 1506
6   UIKit                               0x000000010e8206d8 -[UIViewController _loadViewFromNibNamed:bundle:] + 242
7   UIKit                               0x000000010e820cc8 -[UIViewController loadView] + 109
8   UIKit                               0x000000010e820f39 -[UIViewController loadViewIfRequired] + 75
9   UIKit                               0x000000010e8213ce -[UIViewController view] + 27
10  UIKit                               0x000000010e73c289 -[UIWindow addRootViewControllerViewIfPossible] + 58
11  UIKit                               0x000000010e73c64f -[UIWindow _setHidden:forced:] + 247
12  UIKit                               0x000000010e748de1 -[UIWindow makeKeyAndVisible] + 42
13  UIKit                               0x000000010e6ec417 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2732
14  UIKit                               0x000000010e6ef19e -[UIApplication _runWithMainScene:transitionContext:completion:] + 1349
15  UIKit                               0x000000010e6ee095 -[UIApplication workspaceDidEndTransaction:] + 179
16  FrontBoardServices                  0x00000001114b95e5 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 21
17  CoreFoundation                      0x000000010dd8541c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
18  CoreFoundation                      0x000000010dd7b165 __CFRunLoopDoBlocks + 341
19  CoreFoundation                      0x000000010dd7af25 __CFRunLoopRun + 2389
20  CoreFoundation                      0x000000010dd7a366 CFRunLoopRunSpecific + 470
21  UIKit                               0x000000010e6edb02 -[UIApplication _run] + 413
22  UIKit                               0x000000010e6f08c0 UIApplicationMain + 1282
23  Patient Consent Project             0x000000010dc3fe97 main + 135
24  libdyld.dylib                       0x00000001100f2145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

这是我认为 UIPickerView 的代码：

class ProcedurePicker: UIViewController, UIPickerViewDelegate {

var selectedText = "Pick Procedure Here"
var procedures = ["Epidural Steroid Injection", "Selective Nerve Root Injection", "Facet Joint Injection", "Medial Branch Nerve Block", "Sympathetic Nerve Block", "Caudal Epidural Injection", "Intrathecal Opioid Injection", "Epidural Blood Patch", "Radiofrequency Ablation on Medial Branch Nerve", "Spinal Cord Stimulator Trial", "Piriformins Injection", "Tail Bone Injection", "Ganglion Impar Block", "Stellate Ganglion Block", "Discography"]
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int{
  return 1
}
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return procedures.count
}

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    return procedures[row]
}

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
{
    selectedText = procedures[row]
}

@IBAction func onPressDone(sender: UIButton) {
    ProcedureButtonText = selectedText
}

}

我是 Swift 和 iOS 的新手，所以您能否也解释一下发生了什么以及为什么会发生此崩溃？

Answer 1

通常的原因是，在您的情节提要中的某处，您有一个 link 到代码中不再存在的插座。在这种情况下，它似乎被称为picker。

这可能是因为更改代码而没有考虑代码外部对它的自动引用。

检查故事板对象是否存在不再有效的连接。

Answer 2

大多数时候，这是因为您在故事板中有出路link，而这个出路已不存在 在视图控制器文件中。检查是否是这种情况（使用您的选择器）。

为此，打开你的故事板，点击那个特定的 UI（在你的情况下是选择器），检查它是否连接到某个插座（你可以如图所示检查它）。如果是，则使用叉号将其删除。希望你的错误会得到解决。如果您需要此插座，请在您的视图控制器文件中添加该方法。

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