针对另一个模型验证表单字段

Question

我正在尝试建立一个允许用户对列表进行投标的拍卖网站。为了让用户成功出价，他们必须输入高于当前最高出价的金额，如果由于还没有用户出价而没有当前最高出价，则第一个出价输入必须高于上市起始价格。

如果输入不符合这些条件，我想向我的 BidForm 添加表单验证以引发错误，但我在 def clean_bid_input 中的 listing.id 上有一个 pylint 错误，它说它是一个未定义的变量，所以我觉得我的表单验证不太正确。请有人看看我的表单验证是否符合我希望的逻辑？

models.py

class Listing(models.Model):

    class NewManager(models.Manager):
        def get_queryset(self):
            return super().get_queryset().filter(status='active')

    options = (
        ('active', 'Active'),
        ('closed', 'Closed'),
    )

    title = models.CharField(max_length=64)
    description = models.TextField(max_length=64)
    start_price = models.DecimalField(max_digits=9, decimal_places=2, validators=[MinValueValidator(0.99)])
    image = models.URLField(max_length=200, blank=True)
    category = models.ForeignKey(Category, on_delete=models.CASCADE, related_name="listings")
    lister = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, default=None, null=True, blank=True, related_name="lister_user")
    date_added = models.DateTimeField(default=timezone.now)
    status = models.CharField(max_length=10, choices=options, default="active")
    winner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.SET(get_sentinel_user), related_name="winner_user", null=True)
    favourites = models.ManyToManyField(User, related_name="favourite", default=None, blank=True)
    objects = models.Manager()
    listingmanager = NewManager()

    def __str__(self): 
        return f"{self.title} ({self.pk}, £{self.start_price}, {self.lister})"    


class Bid(models.Model):
    bidder = models.ForeignKey(User, on_delete=models.CASCADE, related_name="bidders")
    bid_item = models.ManyToManyField(Listing, related_name="bid_items", default=None)
    bid_input = models.DecimalField(max_digits=9, decimal_places=2, default=None)
    time = models.DateTimeField(default=timezone.now)

    def __str__(self):
        return f"Bid amount: {self.bid_input}"

forms.py

class NewListingForm(forms.ModelForm):
    class Meta:
        model = Listing
        fields = ["title", "description", "start_price", "image", "category"]

    title = forms.CharField(widget=forms.TextInput(attrs={'autocomplete':'off'}))
    description = forms.CharField(widget=forms.TextInput(attrs={'autocomplete':'off'}))
    start_price = forms.DecimalField(label='Starting Bid Price (£)')
    image = forms.URLField(widget=forms.URLInput(attrs={'autocomplete':'off'}))
    category = forms.ModelChoiceField(queryset=Category.objects.all())
    

class BidForm(forms.ModelForm):
    class Meta:
        model = Bid
        fields = ["bid_input"]
        labels = {"bid_input": ""}
        widgets = {
            "bid_input": forms.NumberInput(attrs={'placeholder': 'Enter bid (£)'})
        }
    
    def clean_bid_input(self):
        data = self.cleaned_data['bid_input']
        highest_bid = Bid.objects.filter(bid_item=listing.id).aggregate(Max('bid_input'))
        listing_price = Listing.start_price.get(bid_item=listing.id)
        if highest_bid is None:
            if data < listing_price:
                raise ValidationError('Bid must be higher than listing start price')
        if data < highest_bid:
            raise ValidationError('Bid must be higher than current highest bid')

Answer 1

在clean_bid_input 方法中替换这个：

listing_price = Listing.start_price.get(bid_item=listing.id)

有了这个

listing_price = Listing.objects.get(bid_item=listing.id).start_price