问题描述
我正在尝试发送一个表单,该表单将使用Django在我的表Listing中添加一个新的“项目” /行。
我确定问题在于我正在使用ForeignKey并继续收到以下错误:
ValueError: Cannot assign "'2'": "Listing.category" must be a "Category" instance.
请注意,上面的值2只是我拥有的7个选项之一。
我在Models.py中定义的“类别”表当前按以下方式填充:
(id) : (category)
7 : Book
6 : Technology
5 : Beauty
4 : Clothing
3 : Health
2 : Sports
1 : Grocery
Models.py:
class Category(models.Model):
category = models.CharField(max_length=16)
def __str__(self):
return f"{self.id} : {self.category}"
class Listing(models.Model):
owner = models.CharField(max_length=64)
title = models.CharField(max_length=64)
description = models.CharField(max_length=256)
startingBid = models.IntegerField()
link = models.CharField(max_length=1024,blank=True)
category = models.ForeignKey(Category,on_delete=models.CASCADE,related_name="category_id")
time = models.DateTimeField(auto_Now_add=True)
def __str__(self):
return f'"{self.title}" added by {self.owner}'
Views.py
class Create(forms.Form):
CHOICES = (
(1,'Grocery'),(2,'Sports'),(3,'Health'),(4,'Clothing'),(5,'Beauty'),(6,'Technology'),(7,'Book'),)
owner = forms.CharField(widget=forms.TextInput(attrs={'placeholder': 'Your Username'}))
title = forms.CharField(widget=forms.TextInput(attrs={'placeholder': 'What is your item?'}))
description = forms.CharField(widget=forms.Textarea(attrs={'placeholder': 'Max 256 characters'}))
link = forms.URLField(required=False)
startingBid = forms.IntegerField()
category = forms.ChoiceField(choices=CHOICES)
@login_required
def create_listing(request):
if request.method == "POST":
form = Create(request.POST)
if form.is_valid():
owner = form.cleaned_data["owner"]
title = form.cleaned_data["title"]
description = form.cleaned_data["description"]
link = form.cleaned_data["link"]
startingBid = form.cleaned_data["startingBid"]
category = form.cleaned_data["category"]
item = Listing(owner=owner,title=title,description=description,link=link,startingBid=startingBid,category=category)
item.save()
else:
return render(request,"auctions/create_listing.html",{
"create": Create()
})
出于故障排除的目的,我手动对类别的ID或英语单词进行了硬编码,而不是传递category = category(例如,category ='Sports'或category ='4'),但这不能解决问题。
我也浏览了几篇类似的文章,但最终无法提出建议。
我确定我的问题很基本,但是我似乎无法理解问题的根本原因。
期待得到您的帮助!
解决方法
尝试一下:
item = Listing(owner=owner,title=title,description=description,link=link,startingBid=startingBid,category_id=category)
类别需要一个对象,而您传递的是id,因此如果传递的是id,category_id
应该可以解决问题。
如果要通过类别选择,则应该尝试:
item = Listing(owner=owner,category__category=category)
,
在模型列出 类别中是一个外键,由于错误提示,您应该存储类别的实例。
尝试一下:
category = Category.object.filter(id = form.cleaned_data["category"]).first()
item = Listing(owner=owner,category=category)