ValueError：无法在 django 中分配答案

【问题标题】：ValueError: Cannot assign in djangoValueError：无法在 django 中分配
【发布时间】：2012-01-08 14:42:09
【问题描述】：

我在尝试向模型添加/发布数据时遇到问题。这就是我在 python manage.py shell 中所做的：

>>> from booking.models import *
>>> qa = Product.objects.get(id=5)
>>> sd = Booking.objects.create(
... date_select = '2011-11-29',
... product_name = qa.name,
... quantity = 1,
... price = qa.price,
... totalcost = 20,
... first_name = 'lalala',
... last_name = 'sadsd',
... contact = '2321321',
... product = qa.id)
Traceback (most recent call last):
  File "<console>", line 10, in <module>
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 138, in create
    return self.get_query_set().create(**kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 358, in create
    obj = self.model(**kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 352, in __init__
    setattr(self, field.name, rel_obj)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py", line 331, in __set__
    self.field.name, self.field.rel.to._meta.object_name))
ValueError: Cannot assign "5": "Booking.product" must be a "Product" instance.

我不知道为什么会这样…… product = qa.id 不等于 Booking.product？

这是我的model.py

from django.db import models

# Create your models here.
class Product(models.Model):
    name = models.CharField(max_length=50, null=True, unique=False)
    quantity = models.IntegerField(max_length=10, null=True)
    price = models.FloatField()
    def __unicode__(self):
        return self.name

class Booking(models.Model):
    date_select = models.DateField(auto_now=False, auto_now_add=False)
    product_name = models.CharField(max_length=50, blank=True, null=True)
    quantity = models.IntegerField(max_length=10, blank=True, null=True)
    price = models.FloatField()
    totalcost = models.FloatField()
    first_name = models.CharField(max_length=50, null=True, blank=True, unique=False)
    last_name = models.CharField(max_length=50, null=True, blank=True, unique=False)
    contact = models.CharField(max_length=50, null=True, blank=True, unique=False)
    product = models.ForeignKey(Product)
    def __unicode__(self):
        return self.first_name

还有我的 handlers.py

from django.utils.xmlutils import SimplerXMLGenerator
from piston.handler import BaseHandler
from booking.models import *
from piston.utils import rc, require_mime, require_extended, validate
class BookingHandler(BaseHandler):
    allowed_method = ('GET', 'POST', 'PUT', 'DELETE')
    fields = ('id', 'date_select', 'product_name', 'quantity', 'price','totalcost', 'first_name', 'last_name', 'contact', 'product')
    model = Booking

    def read(self, request, id):
        if not self.has_model():
            return rc.NOT_IMPLEMENTED
        try:
            inst = self.model.objects.get(id=id)
            return inst
        except self.model.MultipleObjectsReturned:
            return rc.DUPLICATE_ENTRY
        except self.model.DoesNotExist:
            return rc.NOT_HERE

    def create(self, request, *args, **kwargs):
        if not self.has_model():
            return rc.NOT_IMPLEMENTED

        attrs = self.flatten_dict(request.POST)
        if attrs.has_key('data'):
            ext_posted_data = SimplerXMLGenerator(request.POST.get('data'))
            attrs = self.flatten_dict(ext_posted_data)
        try:
            inst = self.model.objects.get(**attrs)
            return rc.DUPLICATE_ENTRY
        except self.model.DoesNotExist:
            inst = self.model(**attrs)#error??
            inst.save()
            return inst
        except self.model.MultipleObjectsReturned:
            return rc.DUPLICATE_ENTR

有人可以帮我了解一下我的情况吗？

提前谢谢...

【问题讨论】：

标签： python xml django django-piston

【解决方案1】：

product = qa

使用 ForeingKey 你应该分配一个对象，而不是 id。

【讨论】：

因为您可以使用sd.product 引用它，您将获得完整的 Product 对象

【解决方案2】：

您将产品指定为

product = qa.id

虽然你应该这样做

product = qa

【讨论】：