使用非表单数据进行Django ModelForm验证

Question

我是Django（1.9.6）的新手，我正在努力了解是否可以验证ModelForm上需要引用引用模型外键中包含的信息的字段。

如何验证用户在OrderForm上为"num_tickets"输入的值是否小于或等于通过外键关系连接的Event类上的"tickets_maining"字段？

我不想在OrderForm上暴露Order类的Event字段，因为用户已经访问了特定的事件页面，并且已经选择购买门票。

型号.py

class Order(models.Model):
    first_name = models.CharField('First Name', max_length=120,null=False, blank=False)
    last_name = models.CharField('Last Name', max_length=120, null=False, blank=False)
    email = models.EmailField('Email', null=False, blank=False)
    event = models.ForeignKey(Event)
    num_tickets = models.PositiveIntegerField('Tickets', null=False, blank=False, validators=[MinValueValidator(0)])
    total_price = models.DecimalField('Total', max_digits=8, decimal_places=2, default=0.0)
    timestamp = models.DateTimeField(auto_now_add=True, auto_now=False)
class Event(models.Model):
    event_name = models.CharField(max_length=200)
    price = models.DecimalField(max_digits=8, decimal_places=2, default=00.00, validators=[MinValueValidator(0)])
    tickets_remaining = models.PositiveIntegerField(default=300)

Forms.py

class OrderForm(forms.ModelForm):
class Meta:
    model = Order
    fields = ['first_name', 'last_name', 'email', 'num_tickets']
def clean_num_tickets(self):
    tickets = self.cleaned_data["num_tickets"]
    # validation Logic. Want to ensure a user cannot purchase more
    # tickets than what an event has for "tickets_remaining"
    return tickets

Answer 1

您没有首先显示如何将订单与事件关联起来。如果你还没有做到这一点，那么你的问题不仅仅是验证可用的门票。

我建议将该事件从视图传递到表单实例化中。然后，您可以使用它将订单与该事件关联起来，并验证票证。

class OrderForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        self.event = kwargs.pop('event', None)
        super(OrderForm, self).__init__(*args, **kwargs)
    def clean_num_tickets(self):
        tickets = self.cleaned_data["num_tickets"]
        if tickets > self.event.tickets_remaining:
            raise ValidationError('Too many tickets')
        return tickets
    def save(self, commit=False):
        order = super(OrderForm, self).save(commit=False)
        order.event = self.event
        if commit:
            order.save()
        return commit

现在，在实例化事件时将其传递到表单中：

form = OrderForm(request.POST, event=event)