在 CoreData 中设置值会使应用程序崩溃
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【中文标题】在 CoreData 中设置值会使应用程序崩溃【英文标题】：Setting a value in CoreData crashes application 【发布时间】：2018-04-03 02:58:21 【问题描述】：好的，所以我进行了大量搜索，我发现的所有内容似乎都与视图控制器有关，并且它们上的链接不起作用或未连接。那不是我的问题。我有一个应用程序，它使用 CoreData 在表格列表、表格编号、它们是否干净以及它们是否正在使用中保持标签。但是，当我尝试使用 setValue() 函数更改属性的键值时，它会使我的应用程序崩溃，并显示以下崩溃报告
2018-04-02 21:45:15.840265-0500 Trakr[26636:1455153] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<NSManagedObjectContext 0x6040001c4fb0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key inUse.'
*** First throw call stack:
(
0 CoreFoundation 0x000000010d1af1e6 __exceptionPreprocess + 294
1 libobjc.A.dylib 0x0000000108f3d031 objc_exception_throw + 48
2 CoreFoundation 0x000000010d1af0b9 -[NSException raise] + 9
3 Foundation 0x000000010895eb47 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 292
4 Trakr 0x0000000108615bee _T05Trakr24CheckTableViewControllerC18inUseSwitchChangedyypF + 846
5 Trakr 0x0000000108615e41 _T05Trakr24CheckTableViewControllerC18inUseSwitchChangedyypFTo + 81
6 UIKit 0x000000010ac1a448 -[UIApplication sendAction:to:from:forEvent:] + 83
7 UIKit 0x000000010ad95804 -[UIControl sendAction:to:forEvent:] + 67
8 UIKit 0x000000010ad95b21 -[UIControl _sendActionsForEvents:withEvent:] + 450
9 UIKit 0x000000010b8d6d60 -[UISwitchModernVisualElement sendStateChangeActions] + 73
10 UIKit 0x000000010b29889f -[UISwitchMVEGestureTrackingSession _sendStateChangeActionsIfNecessary] + 63
11 UIKit 0x000000010b8d74ec -[UISwitchModernVisualElement _handleLongPressWithGestureLocationInBounds:gestureState:] + 760
12 UIKit 0x000000010b21141b -[UIGestureRecognizerTarget _sendActionWithGestureRecognizer:] + 57
13 UIKit 0x000000010b21a1f0 _UIGestureRecognizerSendTargetActions + 109
14 UIKit 0x000000010b217a38 _UIGestureRecognizerSendActions + 307
15 UIKit 0x000000010b216c8c -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 859
16 UIKit 0x000000010b1fbcf0 _UIGestureEnvironmentUpdate + 1329
17 UIKit 0x000000010b1fb773 -[UIGestureEnvironment _deliverEvent:toGestureRecognizers:usingBlock:] + 484
18 UIKit 0x000000010b1fa875 -[UIGestureEnvironment _updateGesturesForEvent:window:] + 281
19 UIKit 0x000000010ac9080b -[UIWindow sendEvent:] + 4064
20 UIKit 0x000000010ac34370 -[UIApplication sendEvent:] + 352
21 UIKit 0x000000010b57557f __dispatchPreprocessedEventFromEventQueue + 2796
22 UIKit 0x000000010b578194 __handleEventQueueInternal + 5949
23 CoreFoundation 0x000000010d151bb1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
24 CoreFoundation 0x000000010d1364af __CFRunLoopDoSources0 + 271
25 CoreFoundation 0x000000010d135a6f __CFRunLoopRun + 1263
26 CoreFoundation 0x000000010d13530b CFRunLoopRunSpecific + 635
27 GraphicsServices 0x000000010fa46a73 GSEventRunModal + 62
28 UIKit 0x000000010ac190b7 UIApplicationMain + 159
29 Trakr 0x000000010861e697 main + 55
30 libdyld.dylib 0x000000010e318955 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
我终其一生都无法弄清楚为什么会发生这种情况。这是我的视图控制器类：
import UIKit
import CoreData
class CheckTableViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource
@IBOutlet weak var backgroundImage: UIImageView!
@IBOutlet weak var pickerView: UIPickerView!
@IBOutlet weak var tableNumberLabel: UILabel!
@IBOutlet weak var cleanSwitch: UISwitch!
@IBOutlet weak var inUseSwitch: UISwitch!
var tablesList = [Table]()
override func viewDidLoad()
super.viewDidLoad()
pickerView.delegate = self
pickerView.dataSource = self
let fetchRequest: NSFetchRequest<Table> = Table.fetchRequest()
do
let tablesList = try PersistenceService.context.fetch(fetchRequest)
self.tablesList = tablesList
catch
backgroundImage.addBlurEffect()
tableNumberLabel.text = "Select a Table"
cleanSwitch.isEnabled = false
inUseSwitch.isEnabled = false
if tablesList.isEmpty
pickerView.isHidden = true
tableNumberLabel.text = "Add Some Tables"
else
pickerView.isHidden = false
// Do any additional setup after loading the view.
override func didReceiveMemoryWarning()
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
// MARK: - Picker View and Switch Controlls
func numberOfComponents(in pickerView: UIPickerView) -> Int
return 1
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
return tablesList.count
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
return String(tablesList[row].tableNumber)
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
if (tablesList.isEmpty)
tableNumberLabel.text = "Add a table"
else
tableNumberLabel.text = String(tablesList[row].tableNumber)
if cleanSwitch.isEnabled == false
cleanSwitch.isEnabled = true
if inUseSwitch.isEnabled == false
inUseSwitch.isEnabled = true
if tablesList[row].isClean == true
cleanSwitch.isOn = true
else
cleanSwitch.isOn = false
if tablesList[row].inUse == true
inUseSwitch.isOn = true
else
inUseSwitch.isOn = false
@IBAction func cleanSwitchChanged(_ sender: Any)
if cleanSwitch.isOn == false
PersistenceService.context.setValue(false, forKey: "isClean")
else
PersistenceService.context.setValue(true, forKey: "isClean")
@IBAction func inUseSwitchChanged(_ sender: Any)
if inUseSwitch.isOn == false
let selectedRow = pickerView.selectedRow(inComponent: 0)
tablesList[selectedRow].inUse = false
PersistenceService.context.setValue(false, forKey: "inUse")
else
let selectedRow = pickerView.selectedRow(inComponent: 0)
tablesList[selectedRow].inUse = true
PersistenceService.context.setValue(true, forKey: "inUse")
这是我的 PersistenceService 类，负责 CoreData 功能的类
import Foundation
import CoreData
class PersistenceService
// MARK: - Core Data stack
private init()
static var context: NSManagedObjectContext
return persistentContainer.viewContext
static var persistentContainer: NSPersistentContainer =
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "tableModel")
container.loadPersistentStores(completionHandler: (storeDescription, error) in
if let error = error as NSError?
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
)
return container
()
// MARK: - Core Data Saving support
static func saveContext ()
let context = persistentContainer.viewContext
if context.hasChanges
do
try context.save()
print("Saved to CoreData")
catch
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
最后，a screenshot of my tableModel CoreData Model
谁能告诉我为什么这不起作用？我这辈子都无法理解....
【问题讨论】：
这应该是entity instance 而不是 NSManagedObjectContext instance 您设置值的位置。
【参考方案1】：
您应该创建 NSManagedObject 的 Table 子类，而不是使用 KVC。然后你可以直接在“Table”实例中设置值。
另外，您将值设置为context.setValue(:)，您应该首先创建一个Table 的实体描述，如下所示
var newTable = NSEntityDescription.insertNewObject(forEntityName: "Table", into: PersistenceService.context)
newTable.setValue(fale, forKey: "isClean")
【讨论】：
谢谢！但是，我还发现调用 PersistenceService.saveContext() 实际上是在保存数据，尽管据我所知，我还没有修改上下文。这是怎么回事？以上是关于在 CoreData 中设置值会使应用程序崩溃的主要内容，如果未能解决你的问题，请参考以下文章
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