NSFetchedResultsController始终包含临时对象

Question

我有一个NSFetchedResultsController我设置如下:

        let fetchRequest = NSFetchRequest(entityName: "Order")
        fetchRequest.includesPendingChanges = false
        fetchRequest.sortDescriptors = [
            NSSortDescriptor(key: "status", ascending: false),
            NSSortDescriptor(key: "date", ascending: false)]

        self.fetchedResultsController = NSFetchedResultsController(
            fetchRequest: fetchRequest,
            managedObjectContext: DataStoreManager.sharedInstance.mainContext,
            sectionNameKeyPath: "section",
            cacheName: nil)

        do {
            try self.fetchedResultsController.performFetch()

        } catch let error as NSError {
            print(error)
        }

问题是即使includesPendingChanges设置为false,controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?)每次我在上下文中创建一个新对象时仍会调用(不保存).

还有什么我应该寻找以避免这种情况吗？

Answer 1

建议的方法是使用子上下文.父项应该是获取结果控制器中使用的主线程管理对象上下文.

如果保存,更改会立即"推送"到主上下文,即获取的结果控制器.(保存主要上下文以持久存储到持久性存储.)

如果您不想保存,只需丢弃子上下文而不保存.获取的结果控制器永远不会知道它.