核心数据排序使用UITableView和NSOrderedSet [英] Core Data ordering with a UITableView and NSOrderedSet

问题描述

在以Core Data作为后备存储的 UITableViewController 中实现用户定义排序需要执行哪些步骤？

What are the steps that I need to perform to implement user-defined ordering in a UITableViewController with Core Data as the backing store?

我还需要回应 -tableView：moveRowAtIndexPath：fromIndexPath：toIndexPath：由表视图自动处理排序？我可以检查核心数据模型文件中的有序复选框，并期望它将更改从表视图传输到商店，或者我还需要做更多？我必须改变我的 fetchedResultsController 获取它的对象（例如添加一个排序描述符）的方式吗？

Do I still need to respond to -tableView:moveRowAtIndexPath:fromIndexPath:toIndexPath: or is the model re-ordering handled automatically by the table view? Can I just check the "Ordered" checkbox in the Core Data model file and expect it to transmit the changes from the table view to the store, or do I have to do more? Do I have to change the way my fetchedResultsController gets it's objects (e.g. add a sort descriptor)?

推荐答案

您不需要放弃NSFetchedResultsController或NSOrderedSet 。如果你坚持使用NSOrderedSet，简单的方法是只是添加一个方法到你的对象NSManagedObject子类。因此，例如，如果你有一个对象Book有一套有序的Chapters，你可以添加一个方法到Chapters对象：

You don't need to abandon NSFetchedResultsController or NSOrderedSet. If you stick with NSOrderedSet, the easy way is to just add a method to your objects NSManagedObject subclass. So for instance, if you have an object Book with an ordered set of Chapters, you can add a method to the Chapters object:

- (NSUInteger)indexInBookChapters
{
    NSUInteger index = [self.book.chapters indexOfObject:self];
    return index;
}

提示：将此添加到类别，以便CoreData不会覆盖自动生成的代码。

Tip: Add this to a category so it doesn't get overwritten by CoreData auto generated code.

然后，您可以在您的NSFetchedResultsController的排序描述符中使用此方法：

Then you can use this method in your sort descriptor for your NSFetchedResultsController:

fetchRequest.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"indexInBookChapters" ascending:YES]];

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