Question

我正在构建一个通用的FetchedResultsController DataSource类，用于我的所有TableViewControllers，其中一些有多个部分，有些没有（像任何Project一样）。

问题是当Fetched Results Controller有多个部分（ sectionNameKeyPath 不为null）时，如果TableView部分只有一行，didChangeObject上的删除逻辑必须删除整个部分，但是如果在Fetched Results Controller定义（sectionNameKeyPath = nil）上只设置了一个部分，则相同的逻辑不起作用。

任何人都知道如何在didChangeObject上实现泛型删除逻辑以防止出现这种错误？

例外：

从代表处获取了一个例外 NSFetchedResultsController在调用期间 -controllerDidChangeContent :.无效更新：无效的节数。表视图中包含的节数更新（1）必须等于包含的部分数更新前的表视图（1），加号或减号插入或删除的部分（0插入，1删除）。用户信息（空）

//Fetched Results Controller Definition on My Model Class
+ (NSFetchedResultsController*)fetchedResultsController
{
    NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:[self.class entityName]];

    //request.predicate = [NSPredicate predicateWithFormat:@"parent = %@", self];
    request.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"dueDate" ascending:NO]];

    [request setFetchLimit:50];

    //Generate an error
    return [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:Store.defaultManagedObjectContext sectionNameKeyPath:nil cacheName:nil];

    //Works Fine
    //return [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:Store.defaultManagedObjectContext sectionNameKeyPath:@"shortDueDate" cacheName:nil];
}


//Fetched Results Controller Generic Data Source Class
- (void)controller:(NSFetchedResultsController*)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath*)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath*)newIndexPath
{
    if (type == NSFetchedResultsChangeInsert) {
        [self.tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
    } else if (type == NSFetchedResultsChangeMove) {
        [self.tableView moveRowAtIndexPath:indexPath toIndexPath:newIndexPath];
    } else if (type == NSFetchedResultsChangeDelete) {

        BOOL deleteSection = FALSE;

        //If have only one section and its the last row then delete entire section
        if ((self.tableView.numberOfSections == 1) && ([self.tableView numberOfRowsInSection:[indexPath section]] == 1 )) {
            deleteSection = TRUE;
        }

        if (deleteSection) {
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:YES];
        } else {
            [self.tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
        }
    } else {
        NSAssert(NO,@"");
    }
}

Answer 1

如果您实施：

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
       atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type

然后FRC将为您确定是否需要插入或删除部分。

Answer 2

Swift 4.2

在处理NSFEtchedResultsController和CoreData时，我遇到了类似的问题。

覆盖func tableView(_:, commit:, forRowAt:)

override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
    let commit = fetchedResultsController.object(at: indexPath)

    let sections = fetchedResultsController.sections
    let section = sections![indexPath.section]

    // numberOfObjectsInCurrentSection is the class' variable
    numberOfObjectsInCurrentSection = section.numberOfObjects

    container.viewContext.delete(commit)
    saveContext()
  }
}

实施此NSFetchedResultsControllerDelegate方法。这里您将检查以前剩余的项目数所选表格视图的部分，然后删除一行或（如果该部分只有一行左右）

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
 switch type {
 case .delete:
    tableView.beginUpdates()

    if numberOfObjectsInCurrentSection! > 1 {
        tableView.deleteRows(at: [indexPath!], with: .automatic)
    } else {
        let indexSet = NSMutableIndexSet()
        indexSet.add(indexPath!.section)
        tableView.deleteSections(indexSet as IndexSet, with: UITableViewRowAnimation.fade)
    }

    tableView.endUpdates()
default:
    break
}
}

删除Tableview NSFetchedResultsController中的最后一部分行

2 个答案:

Swift 4.2