Question

在我的应用程序中，当我从Web服务刷新实体的内容时，我删除了我的Core Data中的所有记录并插入了所有新记录。但是，很多时候记录不会从上下文中删除，即使我再次调用上下文。因此，当我保存时，旧的保留，并且我最终堆叠在现有的堆叠之上，获得大量重复。我怎样才能完全清除上下文，所以我不需要担心重复？

    var appDelegate = UIApplication.shared.delegate as! AppDelegate
    var context = appDelegate.persistentContainer.viewContext
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "V_ServiceDetails")

    // Clear all
    let request = NSBatchDeleteRequest(fetchRequest: fetchRequest)

    do {
        let result = try context.execute(request)
    } catch {}

    appDelegate = UIApplication.shared.delegate as! AppDelegate
    context = appDelegate.persistentContainer.viewContext

    // Add new ones
    for svc in self.svcs {
        let result = NSEntityDescription.insertNewObject(forEntityName: "V_ServiceDetails", into: context)

        result.setValue(svc.Car_VIN, forKey: "car_VIN")
        result.setValue(svc.Cust_Veh_ID, forKey: "cust_Veh_ID")

        do { try context.save() } catch {}
    }

Answer 1

从Apple docs on batch delete开始，它表示删除是直接在SQL级别完成的。您在内存中的对象中删除 NOT REFLECTED ，因此您需要在删除后更新应用。请参阅链接页面上的执行后更新应用程序部分。

Answer 2

尝试以下功能：

func deleteAll() {

    // Managed Object Context
    let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    // Save the changes of the Managed Object Context before executing the Batch Delete Request
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
        } catch {
            // Error
        }
    }

    // Craete a Fetch Request
    let fetchRequest: NSFetchRequest<ManagedObject> = ManagedObject.fetchRequest()

    // Initiliaze the Batch Delete Request
    let batchDeleteRequest = NSBatchDeleteRequest.init(fetchRequest: fetchRequest as! NSFetchRequest<NSFetchRequestResult>)

    // Configure the Batch Delete Request
    batchDeleteRequest.resultType = .resultTypeCount

    do {

        // Execute the Batch Delete Request
        try managedObjectContext.execute(batchDeleteRequest)

        // Reset the Managed Object Context
        managedObjectContext.reset()

        // try self.fetchedResultsController.performFetch()
        // If you have a Table View? Use this function
        // self.tableView.reloadData()

    } catch {
        // Error
    }
}

Answer 3

这对我有用。

var e = 1
    
    while e <= self.items!.count {
        
        self.context.delete(self.items![e - 1])
        
        // Save the data
        do {
            try self.context.save()
            
        }
        catch {
            
            
        }
        
        e = e + 1
        
        
    }

在NSBatchDeleteRequest之后使用核心数据

3 个答案: