持久存储更改后如何刷新fetchedResultsController

Question

我是编程方面的周末战士，所以我可能做错了什么...

我有一个拆分视图控制器，核心数据，nsfetchedResultsController，它们都很好用。现在，我可以为用户提供一个创建persistentStore.sqlite文件的备份文件的选项。当用户从备份文件还原时，表视图不会反映任何更改。最重要的是，此后不能在tableview的add / delete中进行任何持久的更改。当我退出应用程序并重新启动它时，所有数据都从备份那里备份，并且一切正常。

如何强制tableview从获取的结果控制器中获取最新信息？或者我该如何强迫

以下是到目前为止我没有成功尝试过的内容：

MasterViewController.m

- (void)viewDidLoad
{
    context = [[OSCDStackManager sharedManager] managedObjectContext];
}

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reloadFetchedResults) name:OSFilesUpdatedNotification object:nil];

- (void)reloadFetchedResults:(NSNotification*)note {
    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    if (note) {
        [self.tableView reloadData];
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    NSError *error = nil;
    [self.fetchedResultsController performFetch:&error];
    [self.tableView endUpdates];
    [self.tableView reloadData];
}

从tableview的手动刷新下拉菜单中...

-(void) updateTable{
    context = [[OSCDStackManager sharedManager] managedObjectContext];
    NSError *error = nil;
    [self.fetchedResultsController performFetch:&error];
    //[self.tableView endUpdates];
    [self.tableView reloadData];
    [self.refreshControl endRefreshing];
}

- (void)viewWillAppear:(BOOL)animated  {
    [self.tableView reloadData];
}


- (NSFetchedResultsController *)fetchedResultsController
{
    context = [[OSCDStackManager sharedManager] managedObjectContext];
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    [fetchRequest setFetchBatchSize:20];
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
    NSArray *sortDescriptors = @[sortDescriptor];
    [fetchRequest setSortDescriptors:sortDescriptors];
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:nil cacheName:nil];
    //[NSFetchedResultsController deleteCacheWithName:@"cache"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;
    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    return _fetchedResultsController;
} 

即使这是我邻居的应用程序，我还是不想告诉他在备份后杀死并重新启动该应用程序...

解决方案最终是以下两个答案的结合，

- (void)reloadFetchedResults{
    self.fetchedResultsController = nil;
    [NSFetchedResultsController deleteCacheWithName:@"cache"];
    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    [self.tableView reloadData];
}

Answer 1

消除你的 FRC

-(void)reloadData
{
    NSError *error = nil;
    self.fetchedResultsController = nil;

    if (![self.fetchedResultsController performFetch:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }
    else
        [self.tableView reloadData];

}

** 编辑 ** 如果前面的“自我”不明显，你需要在课堂上的某个地方

-(NSFetchedResultsController *)fetchedResultsController
{
    if (!_fetchedResultsController)
    {
        _fetchedResultsController = [NSFetchedResultsController alloc]initWithFetchRequest:aFetchRequest
                                         managedObjectContext:aManagedObjectContext // the main thread MOC
                                           sectionNameKeyPath:nil cacheName:nil];
            // addional FRC setup etc.

    }

    return _fetchedResultsController;
}