为什么在应用程序重启或我两次执行NSBatchDeleteRequest之前不删除条目？ [英] Why entries are not deleted until app is restarted or I execute my NSBatchDeleteRequest twice?

问题描述

我正在阅读删除/重置核心数据中的所有条目？。

如果执行以下步骤，则会得到意外的结果：

1. 调用下面的代码


2. 然后在模拟器中查询实体，我将获得一个实体！！！


3. 如果我调用 clearCoreDataStore 再次（或重新启动），只有这样才能从核心数据中检索该值

我想念什么？

  func clearCoreDataStore（）{
让实体= dataManager.persistentContainer.managedObjectModel.entities 
用于实体实体{
 let fetchRequest = NSFetchRequest< NSFetchRequestResult>（entityName：entity.name！） ）
}捕获{
 print（error）
} 
} 
 dataManager.saveContext（）
} 
  

解决方案

从持久性存储中删除的对象也可能处于内存对象上下文中。如果是这样，则必须先更新该内存上下文以反映删除。可以在此处找到完整的讨论。 p>

简而言之...

  deleteRequest.resultType = NSBatchDeleteRequestResultType.resultTypeObjectIDs 
 let result =尝试使用context.execute（deleteRequest）作为吗？ NSBatchDeleteResult 
让objectIDArray = result？.result as？ [NSManagedObjectID] 
让更改= [NSDeletedObjectsKey：objectIDArray] 
 NSManagedObjectContext.mergeChanges（fromRemoteContextSave：更改为[context]）
  

I'm reading Delete/Reset all entries in Core Data?.

If I follow the steps below, I get an unexpected result:

1. Call the code below
2. Then query an entity in the simulator, I will get an entity back!!!
3. If I call clearCoreDataStore again (or do a restart), only then the value won't be retrieved from core-data

What am I missing?

func clearCoreDataStore() {
    let entities = dataManager.persistentContainer.managedObjectModel.entities
    for entity in entities {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity.name!)
        let deleteReqest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
        do {
            try context.execute(deleteReqest)
        } catch {
            print(error)
        }
    }
    dataManager.saveContext()
}

解决方案

The objects being deleted from the persistent store are probably also in an in-memory object context. If so, that memory context must first be updated to reflect the deletions. A thorough discussion can be found here.

In a nutshell...

deleteRequest.resultType = NSBatchDeleteRequestResultType.resultTypeObjectIDs
let result = try context.execute(deleteRequest) as? NSBatchDeleteResult
let objectIDArray = result?.result as? [NSManagedObjectID]
let changes = [NSDeletedObjectsKey : objectIDArray]
NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [context])

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