虽然项目正在保存在核心数据中，但在重新启动之前无法查看它们

Question

这是一个示例，其中 FetchedResultsController 在 ViewController 中使用，并且来自另一个 ViewController 的保存没有传递给它。

MainVC.swift

lazy var coreDataManager = CoreDataManager()

// Initialize fetched request
private var fetchRecordRequestController: NSFetchedResultsController = NSFetchedResultsController()

override func viewDidLoad() {
super.viewDidLoad()

// Do any additional setup after loading the view.

// Initialize managedObjectContext
let mainManagedObjectContext = coreDataManager.managedObjectContext

// Create Fetch Request
let fetchRequest = NSFetchRequest(entityName: "Record")

// Configure Fetch Request
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: false)]

// Initialize Fetched Results Controller
fetchRecordRequestController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: mainManagedObjectContext, sectionNameKeyPath: nil, cacheName: nil)

// Configure Fetched Results Controller
fetchRecordRequestController.delegate = self

// Fetch data from object
do {
    try fetchRecordRequestController.performFetch()
} catch let fetchError as NSError {
    print("(RootViewController)fetchError: \(fetchError), \(fetchError.userInfo)")
}

// Add observer in NSNotificationCenter for NSManagedObjectContextObjectsDidChange
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(managedObjectContextObjectsDidChange), name: NSManagedObjectContextObjectsDidChangeNotification, object: mainManagedObjectContext)

override func viewWillDisappear(animated: Bool) {
NSNotificationCenter.defaultCenter().removeObserver(self)
}

// MARK: - NSFetchedResultsController Delegate Methods

func controllerWillChangeContent(controller: NSFetchedResultsController) {
    tableView.beginUpdates()
}

// Delete corresponding row in tableView
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
switch type {
case .Insert:
    tableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Fade)
case .Delete:
    tableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: .Fade)
case .Update:
    tableView.reloadRowsAtIndexPaths([indexPath!], withRowAnimation: .Fade)
case .Move:
    tableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: .Fade)
    tableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Fade)
}
}

func controllerDidChangeContent(controller: NSFetchedResultsController) {
tableView.endUpdates()
}

func managedObjectContextObjectsDidChange(notification: NSNotification) {

let mainManagedObjectContext = coreDataManager.managedObjectContext
guard let userInfo = notification.userInfo else { return }

if let inserts = userInfo[NSInsertedObjectsKey] as? Set<NSManagedObject> where inserts.count > 0 {
    print("--- INSERTS ---")
    print(inserts)
    print("+++++++++++++++")
    do {
        try mainManagedObjectContext.save()
    } catch let saveError as NSError {
        print("(RootViewController)saveError: \(saveError), \(saveError.userInfo)")
    }
}

if let updates = userInfo[NSUpdatedObjectsKey] as? Set<NSManagedObject> where updates.count > 0 {
    print("--- UPDATES ---")
    for update in updates {
        print(update.changedValues())
    }
    print("+++++++++++++++")
}

if let deletes = userInfo[NSDeletedObjectsKey] as? Set<NSManagedObject> where deletes.count > 0 {
    print("--- DELETES ---")
    print(deletes)
    print("+++++++++++++++")
}
}

AddRecordVC.swift

// Method to save the extracted values to CoreData Objects
private func saveValues() {
// Initializing
let mainManagedObjectContext = coreDataManager.managedObjectContext
// Initialize entity description
let RecordDescription = NSEntityDescription.entityForName("Record",inManagedObjectContext:mainManagedObjectContext)
let record = Record(entity: RecordDescription!, insertIntoManagedObjectContext: mainManagedObjectContext)
// Set object values from temporary variables
record.date = dateTemp!
record.tareWeight = tareWeightTemp
record.grossWeight = grossWeightTemp
record.nettWeight = nettWeightTemp
record.numberOfBags = numberOfBagsTemp
record.weightOfBags = weightOfBagsTemp
record.rivaju = rivajuTemp
record.putti = puttiTemp
record.rateOfPaddy = rateOfPaddyTemp
record.amount = amountTemp
// Save the object
do {
    if mainManagedObjectContext.hasChanges {
        try mainManagedObjectContext.save()
    }
} catch let saveError as NSError {
    print("(AddRecordViewController)saveError: \(saveError), \(saveError.userInfo)")
}
}

一旦 AddRuleVC 返回到 RootVC，视图就不会刷新。 但是应用程序退出并重新启动后，它确实显示了数据。单独的class用于CoreDataStack，如下所示。

CoreDataManager.swift

class CoreDataManager: NSObject {

// MARK: - Core Data Stack

lazy var managedObjectModel: NSManagedObjectModel = {
let modelURL = NSBundle.mainBundle().URLForResource("App Name", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
// Create the coordinator and store
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("SingleViewCoreData.sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
    try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
} catch {
    // Report any error we got.
    var dict = [String: AnyObject]()
    dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
    dict[NSLocalizedFailureReasonErrorKey] = failureReason

    dict[NSUnderlyingErrorKey] = error as NSError
    let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
    NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
    abort()
}

return coordinator
}()

lazy var managedObjectContext: NSManagedObjectContext = {
let coordinator = self.persistentStoreCoordinator
var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = coordinator
managedObjectContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
return managedObjectContext
}()

// 标记：- 辅助方法

func saveContext () {
if managedObjectContext.hasChanges {
    do {
        try managedObjectContext.save()
    } catch {
        let nserror = error as NSError
        NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
        abort()
    }
}
}

lazy var applicationDocumentsDirectory: NSURL = {
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1]
}()
}

Answer 1

您的 CoreDataManager class 正在 AddRecordVC 中生成一个新的托管对象上下文，与 MainVC 中的不同，因此当您保存第二个上下文时，持久存储将会更新，但更改不会反映在第一个上下文中，除非您合并更改。

这样不好，主线程只需要一个上下文。所以你应该做的是对托管对象上下文使用依赖注入。当您的应用程序启动时启动 CoreDataManager，然后将上下文注入 MainVC，然后当您转到 AddRecordVC 时，也只需将相同的上下文也传递到那里。

Answer 2

您需要在保存新项目后通过异步执行 tableview.reloadData() 来重新加载您的表格视图。

虽然项目正在保存在核心数据中，但在重新启动之前无法查看它们

Although items are being saved in core data, not able to view them until a relaunch

multithreading

core-data

parent-child

ios

swift