Question

在我的表视图中使用NSFetchedResultsController时，在创建新的NSManagedObject后立即正确显示数据，但更新后将删除所有行/部分。下面，当调用update（）方法并保存联系人时，我的print语句输出正在从表视图中删除行和部分。调用create（）方法时，正在插入行/部分（如预期的那样）。

以下是运行后的两组不同输出：

从API请求中检索到信息后，如果项目已经存在（由唯一ID指定），我将更新相应的核心数据模型，如下所示：

func update(oldContact: NSManagedObject) -> Bool {

    //updates contact
    let contact = populateObject(oldContact)

    // Delete existing phones
    if let phoneDataSet = contact.valueForKeyPath("phones") {
        let phonesArray = phoneDataSet.allObjects as! [NSManagedObject]
        for object in phonesArray {
            context.deleteObject(object)
        }
    }
    // Add phones from response
    for phone in phones {
        phone.createForContact(contact)
    }

    // Save contact
    do {
        try contact.managedObjectContext?.save()
        print("saving contact")
        return true
    } catch {
        let nserror = error as NSError
        print("error upong saving")
        NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
        abort()
    }

    return false
}

  func populateObject(object: NSManagedObject) -> NSManagedObject {

    object.setValue(self.name, forKey: "name")
    object.setValue(self.id, forKey: "id")
    object.setValue(self.firstLetter, forKey: "firstLetter")

    return object
  }

如果该项目在核心数据中已不存在，则会按如下方式创建：

func create() -> Bool {

    // Quit if contact already exists.
    let data = CoreData().searchObject("Contact", predicate: "id", value: String(self.id))
    guard data == nil else { fatalError("Attempted to insert duplicate contact") }

    //creates a new contact NSManagedObject
    var newContact = NSEntityDescription.insertNewObjectForEntityForName("Contact", inManagedObjectContext: context)
    //sets the contact values
    newContact = populateObject(newContact)

    //creates Phone NSManagedObject, then makes a relationship with contact
    for phone in self.phones {
        phone.createForContact(newContact)
    }

    do {
        //saves the contact object; also saves the relationship with the phone number
        try newContact.managedObjectContext?.save()
        print("Creating contact")
        return true;
    } catch {
        let nserror = error as NSError
        NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
        abort()
    }

    return false
}

我的FetchedResultsController委托方法如下所示：

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
    switch (type) {
    case .Update:
        if let indexPath = indexPath {
            if let cell = tableView.cellForRowAtIndexPath(indexPath) as? PeopleAndPlaceCell {
                configureCell(cell, atIndexPath: indexPath)
                tableView.reloadRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Fade)
                print("UPDATING ROW")
            }
        }
        break;
    case .Insert:
        if let indexPath = newIndexPath {
            tableView.insertRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
            print("INSERTING ROW")
        }
        break;
    case .Delete:
        if let indexPath = indexPath {
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
            print("DELETING ROW")
        }
        break;
    case .Move:
        if let indexPath = indexPath {
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        }

        if let newIndexPath = newIndexPath {
            tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
        }
        break;
    }
}

func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
    switch type {
    case .Update:
        print("UPDATE SECTION")
        break
    case .Insert:
        self.tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
        print("INSERTING SECTION")
    case .Delete:
        self.tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
        print("DELETING SECTION")
    case .Move:
        break
    }
}

更新：

联系人与电话的关系是一对多，从电话到联系人是一对一的关系。 Phone实体中联系人关系的删除规则是Cascade。它也是联系人实体中电话关系的级联。

Answer 1

问题是contact实体的Phone关系的“级联”删除规则的结果。在update()方法中，删除给定Phone的所有“旧”Contact个对象。级联删除规则也会导致Contact被删除。将此删除规则更改为“Nullify”。（您可以将phones实体中的反向关系Contact保留为“级联”：当您删除Contact时，它将删除所有关联的Phones）

NSFetchedResultsController正在删除行，而不是在更新Core Data后更新它们

1 个答案: