ios - 如何删除现有记录并在核心数据中添加新数据

Question

以下是我将记录添加到核心数据数据库的代码....pendingShipmentDAO 是一个 NSObjectModel。问题在于，每次单击按钮时都会嵌入新数据。如果我的数据库中已经存在数据并插入新数据，我如何清除数据库中数据中的所有记录？

if((self.pendingShipmentDAO) )
{
    [self.pendingShipmentDAO setValue:shipmentNumber forKey:@"shipmentno"];
    [self.pendingShipmentDAO setValue:proformaInvoiceNumber forKey:@"proforma_invoice_no"];
    [self.pendingShipmentDAO setValue:proformaInvoiceDate forKey:@"proforma_invoice_date"];
    [self.pendingShipmentDAO setValue:invoiceNo forKey:@"invoice_no"];
    [self.pendingShipmentDAO setValue:invoiceDate forKey:@"invoice_date"];
    [self.pendingShipmentDAO setValue:plannedShipmentDates forKey:@"planned_shipment_date"];
    [self.pendingShipmentDAO setValue:address forKey:@"point_of_contact"];
    [self.pendingShipmentDAO setValue:address forKey:@"empid"];
    [self.pendingShipmentDAO setValue:name forKey:@"products"];
    [self.pendingShipmentDAO setValue:qty forKey:@"quantity"];
    [self.pendingShipmentDAO setValue:rte forKey:@"rate"];
    [self.pendingShipmentDAO setValue:amt forKey:@"amount"];
    [self.pendingShipmentDAO setValue:img forKey:@"product_image"];
    [self.pendingShipmentDAO setValue:pendingStatus forKey:@"status"];
}
else
{
    NSManagedObject *pendingShipment = [NSEntityDescription insertNewObjectForEntityForName:@"PendingShipmentDetails" inManagedObjectContext:context];
    [pendingShipment setValue:shipmentNumber forKey:@"shipmentno"];
    [pendingShipment setValue:proformaInvoiceNumber forKey:@"proforma_invoice_no"];
    [pendingShipment setValue:proformaInvoiceDate forKey:@"proforma_invoice_date"];
    [pendingShipment setValue:invoiceNo forKey:@"invoice_no"];
    [pendingShipment setValue:invoiceDate forKey:@"invoice_date"];
    [pendingShipment setValue:plannedShipmentDates forKey:@"planned_shipment_date"];
    [pendingShipment setValue:address forKey:@"point_of_contact"];
    [pendingShipment setValue:address forKey:@"empid"];
    [pendingShipment setValue:name forKey:@"products"];
    [pendingShipment setValue:qty forKey:@"quantity"];
    [pendingShipment setValue:rte forKey:@"rate"];
    [pendingShipment setValue:amt forKey:@"amount"];
    [pendingShipment setValue:img forKey:@"product_image"];
    [pendingShipment setValue:pendingStatus forKey:@"status"];
}

更新:

这就是我获取数据的方式，

NSFetchRequest *request = [[NSFetchRequest alloc]initWithEntityName:@"PendingShipmentDetails"];


    NSEntityDescription *entity = [NSEntityDescription entityForName:@"PendingShipmentDetails" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSError *error = nil;
    NSArray *result = [self.managedObjectContext executeFetchRequest:request error:&error];
    if (result.count > 0) {
        int i;
        amountArray = [[NSMutableArray alloc] init];
        statusArray = [[NSMutableArray alloc]init];
        shipmentReferenceNumberArray = [[NSMutableArray alloc]init];
        invoiceNumberArray = [[NSMutableArray alloc]init];
        for (i = 0; i < [result count]; i++) {
            //NSLog(@"%@", result);
            pending = (NSManagedObject *)[result objectAtIndex:i];
                        NSLog(@"pro inv no %@",[pending valueForKey:@"proforma_invoice_no"]);
                        NSLog(@"shipment no %@",[pending valueForKey:@"shipmentno"]);
                        NSLog(@"pro inv date %@",[pending valueForKey:@"proforma_invoice_date"]);
                        NSLog(@"inv no %@",[pending valueForKey:@"invoice_no"]);
                        NSLog(@"inv date %@",[pending valueForKey:@"invoice_date"]);
                        NSLog(@"pl sh date %@",[pending valueForKey:@"planned_shipment_date"]);
                        NSLog(@"pt ct %@",[pending valueForKey:@"point_of_contact"]);
                        NSLog(@"pro %@",[pending valueForKey:@"products"]);
                        NSLog(@"qty %@",[pending valueForKey:@"quantity"]);
                        NSLog(@"rte %@",[pending valueForKey:@"rate"]);
                        NSLog(@"amt %@",[pending valueForKey:@"amount"]);
                        NSLog(@"pro imng %@", [pending valueForKey:@"product_image"]);
                        NSLog(@"statsus %@", [pending valueForKey:@"status"]);

            // amountArray = [[NSMutableArray alloc]initWithObjects:[pending valueForKey:@"amount"], nil];
            [amountArray addObject:[pending valueForKey:@"amount"]];
            [statusArray addObject: [pending valueForKey:@"status"]];
            [shipmentReferenceNumberArray addObject:[pending valueForKey:@"shipmentno"]];
            [invoiceNumberArray addObject:[pending valueForKey:@"invoice_no"]];

        }

    }

Answer 1

在同一托管对象上下文中同步执行操作(删除、插入)。

1. 您需要使用以下并发类型之一创建托管对象上下文 (MOC):NSPrivateQueueConcurrencyType 或 NSMainQueueConcurrencyType，具体取决于您的需要。

2. 使用performBlockAndWait:做事

   [context performBlockAndWait:^{
   
       // remove all rows    
       NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"PendingShipmentDetails"];
       NSError *error;
       NSArray * pendingShipments = [context executeFetchRequest:request error:&error];
       for (NSManagedObject *pendingShipment in pendingShipments) {
           [context deleteObject: pendingShipment];
       }
   
       // add new row(s)
   
       NSManagedObject *pendingShipment = [NSEntityDescription insertNewObjectForEntityForName:@"PendingShipmentDetails" inManagedObjectContext:context];
   
       // TODO: set values here (e.g. [pendingShipment setValue:...)
   
       // save MOC
       if ([context hasChanges]) {
           (void)[context save:&error];
       }
   }];
   

注意:如果您需要在 block 内引用MOC，请使用context。

参见 Core Data Programming Guide: Concurrency了解详情。