"<CustomerOrder: admin>" 需要有字段 "id" 的值才能使用这种多对多关系答案

【问题标题】："<CustomerOrder: admin>" needs to have a value for field "id" before this many-to-many relationship can be used"<CustomerOrder: admin>" 需要有字段 "id" 的值才能使用这种多对多关系
【发布时间】：2021-03-29 13:58:35
【问题描述】：

我想为我的订单代购。但我收到一个错误，因为它是“ManytoMany”字段。

views.py：

    orderform = OrderForm()
if request.method == 'POST':
    orderform = OrderForm(request.POST)
    if orderform.is_valid() and int(orderform["customer"].value()) == customer[0].id:
        test = orderform.save(commit=False)
        orderitems = OrderItem.objects.filter(customer_id=customer[0].id)
        test.orderitem.add(orderitems )
        orderform.save()
        return redirect('home')

models.py

class CustomerOrder(models.Model):
customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
orderitem = models.ManyToManyField(OrderItem, related_name="orderitem")
dealer = models.ForeignKey(Dealer, default=1, on_delete=models.CASCADE)
status = models.CharField(
    max_length=200,
    choices=WORK_STATUS,
    default="Waiting",
)
pay_method = models.CharField(
    max_length=2,
    choices=PAY_METHOD,
    default=1,
)

【问题讨论】：

标签： django django-forms

【解决方案1】：

首先您必须将记录保存在数据库中，然后将项目添加到 manyTomany。您可以在 documentation 中看到发生在您身上的示例。

以下是可以使用以下命令执行的操作示例 Python API 工具。

创建一些出版物：

>>> p1 = Publication(title='The Python Journal')
>>> p1.save()
>>> p2 = Publication(title='Science News')
>>> p2.save()
>>> p3 = Publication(title='Science Weekly')
>>> p3.save()

创建文章：

>>> a1 = Article(headline='Django lets you build Web apps easily')

在保存之前，您不能将其与出版物关联：

>>> a1.publications.add(p1)
Traceback (most recent call last):
...
ValueError: "<Article: Django lets you build Web apps easily>"
needs to have a value for field "id" before this many-to-many
relationship can be used.

保存！

>>> a1.save()

将文章与出版物相关联：

>>> a1.publications.add(p1)

您的代码应如下所示

    orderform = OrderForm()
if request.method == 'POST':
    orderform = OrderForm(request.POST)
    if orderform.is_valid() and int(orderform["customer"].value()) == customer[0].id:
        test = orderform.save(commit=False)
        orderitems = OrderItem.objects.filter(customer_id=customer[0].id)
        orderform.save()
        test.orderitem.add(orderitems )  # <- after save
        return redirect('home')

【讨论】：