iphone - NSFetchedResultsControllerDelegate 未触发

Question

我无法弄清楚为什么当我向底层数据存储添加数据时，NSFetchedResultsControllerDelegate 方法没有触发。如果我重新启动 iPhone 应用程序，数据会立即显示。

我已经子类化了 UITableViewController 并符合 NSFetchedResultsControllerDelegate:

@interface ProjectListViewController : UITableViewController <NSFetchedResultsControllerDelegate> {
    NSFetchedResultsController* fetchedResultsController_;
    NSManagedObjectContext* managedObjectContext_;
}

我实例化 NSFetchedResultsController 并将委托(delegate)设置为 self:

// Controller
fetchedResultsController_ = [[NSFetchedResultsController alloc] initWithFetchRequest:request
    managedObjectContext:self.managedObjectContext 
                                                                  sectionNameKeyPath:@"Client" 
                                                                           cacheName:@"ProjectsCache"];
fetchedResultsController_.delegate = self;

我实现委托(delegate)方法:

- (void)controllerWillChangeContent:(NSFetchedResultsController*)controller {
    NSLog(@"ProjectListViewController.controllerWillChangeContent");
    // The fetch controller is about to start sending change notifications, so prepare the table view for updates.
    [self.tableView beginUpdates];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController*)controller { ... }
- (void)controller:(NSFetchedResultsController*)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { ... }
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type { ... }

我创建了我想要保存的实体:

Project* newProject = [NSEntityDescription insertNewObjectForEntityForName:@"Project" inManagedObjectContext:self.managedObjectContext];
ProjectDetailViewController* detail = [[ProjectDetailViewController alloc] initWithStyle:UITableViewStyleGrouped 
                                                                                delegate:self 
                                                                                selector:@selector(finishedAdding:) 
                                                                                 project:newProject];

然后，我保存它:

- (void)save {
    // NSLog(@"ProjectDetailViewController.save");
    self.project.name = projectNameTextField_.text; 
    NSError* error;
    BOOL b = [self.project.managedObjectContext save:&error];
    if (!b) {
        NSLog(@"Error saving project!");
    } else {
        NSLog(@"Project was successfully saved.");
        [delegate_ performSelector:selector_ withObject:self.project];
    }
    [self dismissModalViewControllerAnimated:YES];
}

除了我的委托(delegate)方法不触发之外，一切都工作得很好。显然我的表格 View 没有更新，查看新数据的唯一方法是显式刷新或重新启动应用程序。

我浏览了 CoreData Recipe 应用程序 - 但似乎找不到我缺少的内容。想法？

-路德

Answer 1

如果我在创建原始 fetchedResultsController_ 时将 sectionNameKeyPath 从 @"Client"更改为 nil，则 Project 实体创建和保存确实调用了委托(delegate)方法!

fetchedResultsController_ = 
    [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                        managedObjectContext:self.managedObjectContext 
                                          sectionNameKeyPath:nil
                                                   cacheName:@"ProjectsCache"];

经过严格审查，这就是 CoreData Recipes 示例的作用。随着我的数据变得越来越复杂 - 我认为我将需要该参数来帮助将结果分成几个部分，但现在，很高兴看到委托(delegate)处理程序被调用。