ios - 使用带 NSBatchDeleteRequest 的 NSFetchedResultsController

Question

我在使用 NSBatchDeleteRequest 后从 NSFetchedResultsControllerDelegate 获取准确更新时遇到问题，更改作为更新类型而不是 didChange 委托(delegate)方法上的删除类型出现。有没有办法让更改以删除的形式出现？ (对于删除和更新，我有不同的方案)。

删除请求:(使用调用者提供的私有(private)上下文)

fileprivate class func deletePeopleWith(ids: Set<Int>, usingContext context: NSManagedObjectContext) {

    let fr: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Person")

    var predicates: [NSPredicate] = []
    ids.forEach {

        predicates.append(NSPredicate(format: "id = %ld", $0))
    }

    fr.predicate = NSCompoundPredicate(orPredicateWithSubpredicates: predicates)

    let dr = NSBatchDeleteRequest(fetchRequest: fr)
    dr.affectedStores = context.parent?.persistentStoreCoordinator?.persistentStores

    do {

        try context.parent?.execute(dr)
        context.parent?.refreshAllObjects()
        print("Deleting person")

    } catch let error as NSError {

        let desc = "Could not delete person with batch delete request, with error: \(error.localizedDescription)"
        debugPrint(desc)
    }

}

结果:

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {

    DispatchQueue.main.async {

        let changeDesc = "Have change with indexPath of: \(indexPath), new index path of: \(newIndexPath) for object: \(anObject)"
        var changeType = ""
        switch type {

        case .delete:
            changeType = "delete"

        case .insert:
            changeType = "insert"

        case .move:
            changeType = "move"

        case .update:
            changeType = "update"

        }

        print(changeDesc)
        print(changeType)
    }

}

打印:

Have change with indexPath of: Optional([0, 0]), new index path of: Optional([0, 0]) for object: *my core data object*
update

Answer 1

来自 Apple 的 documentation :

Batch deletes run faster than deleting the Core Data entities yourself in code because they operate in the persistent store itself, at the SQL level. As part of this difference, the changes enacted on the persistent store are not reflected in the objects that are currently in memory.

After a batch delete has been executed, remove any objects in memory that have been deleted from the persistent store.

参见 Updating Your Application After Execution用于处理被 NSBatchDeleteRequest 删除的对象的部分。