CODEWITHSUNDEEP
pythondjangodjango-modelsdjango-forms
sarchi-xo
sarchi-xo

Reputation: 246

Validating a form field against another model

I'm trying to build an auctions website that allows users to bid on listings. For a user to successfully place a bid they must input an amount higher than the current highest bid and if there is no current highest bid because no user has placed a bid yet, that first bid input must be higher than the listing start price.

I want to add a form validation to my BidForm to raise an error if the input doesn't fit these conditions but I have a pylint error on listing.id in def clean_bid_input and it says it is an undefined variable so I feel my form validation isn't quite right. Please could someone have a look and see if my form validation is following the logic I'm hoping it will?

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')

Upvotes: 0

Views: 59

Answers (1)

mszan
mszan

Reputation: 558

In clean_bid_input method replace this:

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

with this

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

Upvotes: 1

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