ios - 在核心数据中插入对象后如何重新加载表格视图

Question

我正在尝试通过此代码在 Core Data 中插入一些对象

- (void)insertNewObject: (NSArray *) userInfo // Заносит блюдо в локальную базу данных
{
   for (int i = 0; i < userInfo.count; i++) {
       billContent * bc = [userInfo objectAtIndex:i];
       NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
       NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
       NSManagedObject *nmo = [NSEntityDescription insertNewObjectForEntityForName:[entity name]
                                                                      inManagedObjectContext:context];
       [nmo setValue:CountID forKey:@"billId"];
       [nmo setValue:bc.billAmount forKey:@"courseCount"];
       [nmo setValue:bc.billCourseId forKey:@"courseId"];
       [nmo setValue:bc.billPrice forKey:@"coursePrice"];
       [nmo setValue:bc.billTitle forKey:@"courseTitle"];
       [self saveContext];
   }
}

- (void)saveContext {
   NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
   NSError *error = nil;
   if (![context save:&error]) {
       NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
       abort();
   }
}

如何在我的表格视图中查看这些对象？

在插入后，我试图通过这段代码从核心数据中获取

[self makeAList];

和这里

-(void) makeAList {
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:0];
for (int i = 0; i < [sectionInfo numberOfObjects]; i ++) {
    NSIndexPath *ip = [NSIndexPath indexPathForRow: i inSection:0];
    billContent *bc = [[billContent alloc] init];
    NSManagedObject *mo = [self.fetchedResultsController objectAtIndexPath:ip];
    bc.billId = [[mo valueForKey:@"billId"] description];
    bc.billTitle = [[mo valueForKey:@"courseTitle"] description];
    bc.billPrice = [[mo valueForKey:@"coursePrice"] description];
    bc.billAmount = [[mo valueForKey:@"courseCount"] description];
    bc.depId = [[mo valueForKey:@"departmentId"] description];
    bc.billCourseId = [mo valueForKey:@"courseId"];
    [saved addObject:bc];
}
[countView1 reloadData];

}

但没有任何效果。但是如果我退出这个类，并再次输入它（加载 viewDidLoad）我可以看到新值，我做错了什么？

Answer 1

您应该覆盖 fetchedResultController 中的一些标准方法。看下面的代码：-

 -(void) controllerWillChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView beginUpdates];
}

-(void) controllerDidChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView endUpdates];
}

-(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

UITableView *tableView = self.tableView;

switch (type) {
    case NSFetchedResultsChangeInsert:
        [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeDelete:
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeUpdate: {
        Course *changedCourse = [self.fetchedResultsController objectAtIndexPath:indexPath];
        UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
        cell.textLabel.text = ...;
    }
        break;

    case NSFetchedResultsChangeMove:
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
        [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;
}

}

-(void) controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch (type) {
    case NSFetchedResultsChangeInsert:
        [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
        break;
    case NSFetchedResultsChangeDelete:
        [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
        break;
}

}