使用外键提交Django表单

Question

我正在尝试发送一个表单，该表单将使用Django在我的表列表中添加一个新的“item”/行

我确信问题在于我正在使用外键并不断收到以下错误：

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

我的Models.py中定义的“类别”表当前填写如下：

(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}'

视图.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，我手动硬编码了一个id，或类别的英文单词，而不是传递category=category（例如category='Sports'或category='4'），但这并不能解决问题

我也看过几篇类似的文章，但我无法对我这方面的工作提出建议

我确信我的问题相当基本，但我似乎无法理解问题的根本原因

期待您的帮助

Answer 1

在model列表中，category是一个is外键，正如错误提示的那样，您应该存储category的实例

试试这个：

category = Category.object.filter(id = form.cleaned_data["category"]).first()

item = Listing(owner=owner, title=title, description=description, link=link, startingBid=startingBid, category=category)

Answer 2

试试这个：

item = Listing(owner=owner, title=title, description=description, link=link, startingBid=startingBid, category_id=category)

Category需要一个对象，而您正在传递一个id，因此如果您传递的是它的id，那么category_id应该执行此操作

如果您通过类别选择，则应尝试：

item = Listing(owner=owner, title=title, description=description, link=link, startingBid=startingBid, category__category=category)