如何刪除現有記錄並在核心數據中添加新數據

Question

以下是我的將記錄添加到核心數據數據庫的代碼。...endingShipmentDAO是一個NSObjectModel。 問題是，每次單擊按鈕時，都會嵌入新數據。 如果數據庫中已經存在數據並插入新數據，如何清除數據庫中數據中的所有記錄？

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：

我就是這樣提取數據的，

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

在使用您的實體名稱在核心數據中添加新數據之前，只需調用以下方法即可。

-(void)deleteAllPreviousData {
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Your Entity Name" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];
    NSError *error = nil;
    NSManagedObjectContext *context = [self managedObjectContext];
    NSArray *fetchedObjects = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
    if (fetchedObjects == nil) {
        NSLog(@"Could not delete Entity Objects");
    }
    for (NSManagedObject *currentObj in fetchedObjects) {
        [self.managedObjectContext deleteObject:currentObj];
    }
    [context save:&error];
}

Answer 2

在同一托管對象上下文中同步執行操作（刪除，插入）。

1. 您需要根據並發類型之一創建托管對象上下文（MOC）： NSPrivateQueueConcurrencyType或NSMainQueueConcurrencyType 。

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 (eg [pendingShipment setValue:...) // save MOC if ([context hasChanges]) { (void)[context save:&error]; } }]; 

注意：如果需要在塊內引用MOC，請使用context 。

有關詳細信息，請參見《 核心數據編程指南：並發性 》。