TableView在CoreData更改后不使用FRC Swift 3更新（reloadData） [英] TableView doesn't update(reloadData) after CoreData change using FRC Swift 3

问题描述

我更新了这个问题，因为我发现这个问题的另一个关键。看来，当我添加一些东西到CoreData，tableview不重新加载数据，即使我可以打印出CoreData已保存的对象。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。

这也值得注意，如果我停止应用程序并重新打开它，表视图显示正确的单元格数量和信息。所以看来数据只加载初始构建的属性。

我有一个 UITableView 正在填充 CoreData 并使用 FetchedResultsController 。我添加了FRC委托方法，我试图强制 tableView.reloadData（）方法，但是似乎不工作。

这里是我使用的委托方法：

  func controllerWillChangeContent（_ controller：NSFetchedResultsController< NSFetchRequestResult>）{
 tableView.beginUpdates（）
} 
 
 func controller （_ controller：NSFetchedResultsController< NSFetchRequestResult> ;, didChange anObject：Any，在indexPath：IndexPath？，类型：NSFetchedResultsChangeType，newIndexPath：IndexPath？）{
 
开关类型{
 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我想强制tableview

ViewwillAppear方法：

  override func viewWillAppear （_ animated：Bool）{
 //加载数据
 
 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）
 
 {
 try positiveFetchedResultsController.performFetch（）
} catch let错误为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） ：true）
 negativFetchRequest.sortDescriptors = [negativeSort] 
 negativeFetchedResultsController = NSFetchedResultsController（fetchRequest：negativFetchRequest，managedObjectContext：coreDataStack.managedContext，sectionNameKeyPath：nil，cacheName：nil）
 
 do { 
 try negativeFetchedResultsController.performFetch（）
} catch let错误为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）肯定语句计数）
 print（\（negativeFetchedResultsController.fetchedObjects！.count）negative fetch count ）
 //print(\"\(negativeFetchedResultsController.fetchedObjects![0].statement!.count）negative statements count）
 
 tableView.reloadData（）
} 
  

这里是我的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 ：indexPath）
 cell.personName.text = person.name 
 //print(\"\(person.name！）是名称）
 // 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？十进制
 // print（\（amountTotal！）this is the total）
 cell.statementAmount.text = convertStringToDollarString（amountToConvert：String（描述：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（\ .name！）是名称）
 print（\（person.statement！.count）negative person statement count）
 
 if（person.statement！.count == 0）{
 cell.statementAmount.text =$ 0.00
} 
 else {
 //print(\"\(person.name！）has \（person。语句.count）语句计数）
 let amountTotal = person.value（forKeyPath：statement。@ sum.amountOwed）as？十进制
 print（\（amountTotal！）this is the total）
 cell.statementAmount.text = String（描述：amountTotal！）
 
 cell.statementAmount.text = convertStringToDollarString（amountToConvert：String（描述：amountTotal！））
} 
 
 cell.backgroundColor = Styles.redColor 
 
 let bgColorView = UIView（）
 bgColorView.backgroundColor = Styles.darkRedColor（）
 cell.selectedBackgroundView = bgColorView 
 
默认值：cell.personName。 text =hello
} 
 return cell 
} 
  

解决方案

可以尝试这样：

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

I have updated this question as I found another key to this problem. It seems that when I add something to CoreData, the tableview does not reload the data, even though I can print out the objects that CoreData has saved. So I know the data is correct, but the function func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell never gets called.

It's also worth noting that if I stop the application and reopen it , the table view displays the correct amount of cells and information. So it seems the the data only loads property on initial build.

I have a UITableView that is being populated by CoreData and also using a FetchedResultsController. I added the FRC delegate methods and I tried to force the tableView.reloadData() method, but that doesn't seem to work. The data shows up, if I stop the build and rebuild the project.

Here are my delegate methods that I am using:

    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()
}

When I come back to this View I would like to force the tableview to reload its data.

ViewwillAppear method:

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

    let fetchRequest: NSFetchRequest<Person> = Person.fetchRequest()
    fetchRequest.predicate = NSPredicate(format:"[e-mail] >= 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:"[e-mail] < 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()
}

Here is my cellForRowAt method:

  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: "[e-mail]") 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: "[e-mail]") 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
}

解决方案

maybe try this:

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

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