從查詢集中提取數據

Question

模型.py

class MasterItems(models.Model):

    owner = models.ForeignKey(Teacher, on_delete=models.CASCADE, related_name='ShipperItems_owner')
    name = models.CharField(max_length=255, default="", null=True)

    length = models.FloatField(blank=True, null=True)
    breadth = models.FloatField(blank=True, null=True)
    height = models.FloatField(blank=True, null=True)
    weight = models.FloatField(blank=True, null=True)


class SalesOrderItems(models.Model):
    item = models.ForeignKey(MasterItems, on_delete=models.CASCADE)
    item_quantity = models.IntegerField(default=0)


class SalesOrder(models.Model):

    owner = models.ForeignKey(Teacher, on_delete=models.CASCADE, related_name='so_owner')
    client = models.ForeignKey(MasterClient, on_delete=models.CASCADE, related_name='so_client')
    items = models.ManyToManyField(SalesOrderItems, related_name='items_so', blank=True, null=True)

從前端，我收到了例如[4,2] pk銷售訂單，我想提取與這些SalesOrder關聯的項目

我試過的：

        items = []

        for i in sales_orders:

            so_items = SalesOrderItems.objects.filter(items_so=i)
            print("so_items ", so_items)

            items.append(so_items)

但我得到的輸出是這樣的：

items = [<QuerySet [<SalesOrderItems: SalesOrderItems object (4)>, <SalesOrderItems: SalesOrderItems object (5)>]>, <QuerySet [<SalesOrderItems: SalesOrderItems object (1)>]>]

我怎樣才能得到物品的重量？ 實際上 SalesOrderItems 有 item_quantity，我想將該數量與項目重量相乘以獲得項目的總重量

Answer 1

請嘗試以下操作：

做一個單一的查詢（可選，這只是一個優化）：

queryset = SalesOrderItems.objects.filter(items_so__pk__in=sales_orders)

然后乘以如下：

from django.db.models import FloatField, F, ExpressionWrapper

items = queryset.annotate(total_weight=ExpressionWrapper(
    F('item_quantity') * F('item__weight'), output_field=FloatField())

查詢集中的每個對象都有一個名為total_weight的新屬性，這就是您需要的值。

for item in items:
    item.total_weight # this is what you are looking for

Answer 2

您可以使用values方法並在要使用的列中包含

items =[]
for i in sales_orders:
  so_items = SalesOrderItems.objects.filter (items_so = i).values(
        'item__name',
        'item_quantity'
    )
  print ("so_items ", so_items) items.append (so_items)