ios - 使用 FRC Swift 3 更改 CoreData 后，TableView 不会更新(reloadData)

Question

我已经更新了这个问题，因为我发现了这个问题的另一个关键。似乎当我向 CoreData 添加内容时，tableview 不会重新加载数据，即使我可以打印出 CoreData 保存的对象。所以我知道数据是正确的，但是函数func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 永远不会被调用。

还值得注意的是，如果我停止应用程序并重新打开它，表格 View 会显示正确数量的单元格和信息。所以看起来数据只在初始构建时加载属性。

我有一个 UITableView，它由 CoreData 填充并且还使用了一个 FetchedResultsController。我添加了 FRC 委托(delegate)方法并尝试强制使用 tableView.reloadData() 方法，但这似乎不起作用。如果我停止构建并重新构建项目，数据就会显示出来。

这是我正在使用的委托(delegate)方法:

    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.beginUpdates()
}

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {

    switch type {
    case .insert:
        tableView.insertRows(at: [newIndexPath!], with: .automatic)
    case .delete:
        tableView.deleteRows(at: [indexPath!], with: .automatic)
    case .update: 
       tableview.reloadData()
    case .move:
        tableView.deleteRows(at: [indexPath!], with: .automatic)
        tableView.insertRows(at: [newIndexPath!], with: .automatic)
    }
}

func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.endUpdates()
}

当我回到这个 View 时，我想强制 TableView 重新加载它的数据。

ViewwillAppear 方法:

override func viewWillAppear(_ animated: Bool) {
    // load the data

    let fetchRequest: NSFetchRequest<Person> = Person.fetchRequest()
    fetchRequest.predicate = NSPredicate(format:"statement.@sum.amountOwed >= 0")
    let sort = NSSortDescriptor(key: #keyPath(Person.name), ascending: true)
    fetchRequest.sortDescriptors = [sort]
    positiveFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: coreDataStack.managedContext, sectionNameKeyPath: nil, cacheName: nil)

    do{
     try positiveFetchedResultsController.performFetch()
     }catch let error as NSError{
        print("Fetching error: \(error), \(error.userInfo)")
    }


    let negativFetchRequest: NSFetchRequest<Person> = Person.fetchRequest()
    negativFetchRequest.predicate = NSPredicate(format:"statement.@sum.amountOwed < 0")
    let negativeSort = NSSortDescriptor(key: #keyPath(Person.name), ascending: true)
    negativFetchRequest.sortDescriptors = [negativeSort]
    negativeFetchedResultsController = NSFetchedResultsController(fetchRequest: negativFetchRequest, managedObjectContext: coreDataStack.managedContext, sectionNameKeyPath: nil, cacheName: nil)

    do{
        try negativeFetchedResultsController.performFetch()
    }catch let error as NSError{
        print("Fetching error: \(error), \(error.userInfo)")
    }

    positiveFetchedResultsController.delegate = self
    negativeFetchedResultsController.delegate = self

    print("\(positiveFetchedResultsController.fetchedObjects!.count) positive fetch count")
    //print("\(positiveFetchedResultsController.fetchedObjects![0].statement!.count) positive statements count")
    print("\(negativeFetchedResultsController.fetchedObjects!.count) negative fetch count")
    //print("\(negativeFetchedResultsController.fetchedObjects![0].statement!.count) negative statements count")

    tableView.reloadData()
}

这是我的 cellForRowAt 方法:

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "personCell", for: indexPath) as! PersonTableViewCell

    switch(indexPath.section) {
    case 0:
        //print("this is section 0")
        let person = positiveFetchedResultsController.object(at: indexPath)
        cell.personName.text = person.name
        //print("\(person.name!) is the name")
        //print("\(person.statement!.count) postive person statement count")

        if(person.statement!.count == 0){
            print("default")
            cell.statementAmount.text = "$0.00"
        }
        else{
            //print("\(person.name!) has \(person.statement!.count) statement count")
            let amountTotal = person.value(forKeyPath: "statement.@sum.amountOwed") as? Decimal
            //print("\(amountTotal!) this is the total")
            cell.statementAmount.text = convertStringToDollarString(amountToConvert: String(describing: amountTotal!))

        }

    case 1:

        print("this is section 1")
        //print("\(negativeFetchedResultsController.object(at: [indexPath.row,0])) objects fetched")
        //print("\(indexPath.section) section number")
        //print("\(indexPath.row) row number")

        let person = negativeFetchedResultsController.fetchedObjects![indexPath.row]
        cell.personName.text = person.name

        print("\(person.name!) is the name")
        print("\(person.statement!.count) negative person statement count")

        if(person.statement!.count == 0){
            cell.statementAmount.text = "$0.00"
        }
        else{
            //print("\(person.name!) has \(person.statement!.count) statement count")
            let amountTotal = person.value(forKeyPath: "statement.@sum.amountOwed") as? Decimal
            print("\(amountTotal!) this is the total")
            cell.statementAmount.text = String(describing: amountTotal!)

            cell.statementAmount.text = convertStringToDollarString(amountToConvert: String(describing: amountTotal!))
        }

        cell.backgroundColor = Styles.redColor();

        let bgColorView = UIView()
        bgColorView.backgroundColor = Styles.darkRedColor()
        cell.selectedBackgroundView = bgColorView

    default: cell.personName.text = "hello"
    }
    return cell
}

Answer 1

也许试试这个:

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    self.tableView.reloadData()
}