iphone - 是否为 Core Data 的获取结果 Controller 实现委托(delegate)

Question

实现四种委托(delegate)方法有什么好处:

• (void)controllerWillChangeContent:(NSFetchedResultsController *) Controller

• (void) Controller :(NSFetchedResultsController *) Controller didChangeSection:(id )sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type

• (void) Controller :(NSFetchedResultsController *) Controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)类型newIndexPath:(NSIndexPath *)newIndexPath

• (void)controllerDidChangeContent:(NSFetchedResultsController *) Controller

而不是实现:

• (void)controllerDidChangeContent:(NSFetchedResultsController *) Controller

感谢任何帮助//:)

Answer 1

当您将 FetchedResultsController 与 TableView 一起使用时，您可以实现这四个委托(delegate)方法来响应对所获取结果所做的每个更改，并在表中发生更改时以动画形式呈现。但是，作为 NSFetchedResultsControllerDelegate documentation 状态:

It may be computationally expensive to animate all the changes. Rather than responding to changes individually (as illustrated in “Typical Use”), you could just implement controllerDidChangeContent: (which is sent to the delegate when all pending changes have been processed) to reload the table view

因此，如果您要做大量更改，您只需实现controllerDidChangeContent 并使用诸如[self.tableView reloadData] 之类的内容立即响应所有更改。