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python - 如何从Django中的其他模型中将数据添加到其列被引用（外国字段）的模型中

问题描述

我正在尝试将数据添加到我的购物车模型中，但出现错误，因为在我尝试输入数据的字段中是引用为 Items 的 ForeignField。
无法分配“9”：“Cart.pid”必须是“items”实例。

这是我的代码：-

视图.py

def add_cart(request):
pid = request.POST.get('cart_id')
quantity = request.POST.get('quantity')
details = items.objects.filter(pk = request.POST.get('cart_id'))
name = None
price = None
for i in details:
    name = i.name
    price = i.price
    pid = i.id
user_id = request.user.id
total = int(quantity)*price
instance = Cart(pid = pid,quantity = quantity,pro_name = name,pro_price = price,user_id = user_id,total = total)

return redirect('home')

模型.py

class items(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=100,default='Item')
desc = models.TextField(max_length=500, default='Best')
price = models.IntegerField()
category = models.CharField(max_length=50,default='Product')
image = models.ImageField(upload_to="media",default='Item Image')

class Cart(models.Model):
pid = models.ForeignKey('items',on_delete=CASCADE,related_name="proid")
name = models.ForeignKey('items',on_delete=CASCADE,related_name="proname")
price = models.ForeignKey('items',on_delete=CASCADE,related_name="proprice")
quantity = models.IntegerField(default=1)
user_id = models.ForeignKey(User,on_delete=CASCADE)
total = models.IntegerField(default=0)

请帮忙！！！

标签： pythondjango

解决方案

当我们在 Django 中使用外键时，可以使用相关对象实例或数据库字段原始值。在您的代码中，您有一个名为pid. 您可以为其分配一个对象实例：

for i in details:
    name = i.name
    price = i.price
    pid = i # <!-- no i.id, i is the object instance
user_id = request.user.id
total = int(quantity)*price
instance = Cart(pid = pid,quantity = quantity,pro_name = name,pro_price = price,user_id = user_id,total = total)

...或将键值 ( i.id)分配给神奇创建的属性pid_id：

for i in details:
    name = i.name
    price = i.price
    pid = i.id
user_id = request.user.id
total = int(quantity)*price
instance = Cart(pid_id = pid,quantity = quantity,pro_name = name,pro_price = price,user_id = user_id,total = total)
# We are ising the raw database value. W read it from `i.id` above.
instance.pid_id = pid

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