保持 django 模型清洁方法验证外键对象并使用 ModelForm 保存

Question

在我的模型的 clean 方法中，我验证是否在外键参展商 is_premium 中给出，并验证他没有超过 MAX_DISCOUNTS_PER_EXHIBITOR 的活动对象。

它在 django admin 中运行良好。添加时和编辑时都一样。

我想让它在我的自定义（非 django-admin）视图中工作。我正在使用模型表单。

第一种方法

我将existor in view 分配给最初commit=False 保存的对象。

它与DoesNotExist 崩溃：折扣没有参展商，因为clean 已执行，但参展商尚未分配。实施它的正确方法应该是什么？

models.py

class Discount(models.Model):
    exhibitor = models.ForeignKey(
        'core_backend.Exhibitor', related_name='discounts')
    is_active = models.BooleanField(default=False, verbose_name=u"Aktywny")
    title = models.TextField(verbose_name=u"Tytuł")

    def clean(self):

        if not self.exhibitor.is_premium:
            raise ValidationError(
                u'Discounts only for premium')

        count = Discount.objects.filter(
            is_active=True,
            exhibitor=self.exhibitor
        ).count()

        if not self.pk:
            # newly added
            count = count + (1 if self.is_active else 0)
        else:
            # edited
            discount = Discount.objects.get(pk=self.pk)
            if discount.is_active and not self.is_active:
                count = count - 1
            elif not discount.is_active and self.is_active:
                count = count + 1

        if count > settings.MAX_DISCOUNTS_PER_EXHIBITOR:
            raise ValidationError(
                u'Max %s active discounts' % (
                    settings.MAX_DISCOUNTS_PER_EXHIBITOR
                )
            )

forms.py

class DiscountForm(forms.ModelForm):

    class Meta:
        model = Discount
        fields = (
            'title',
            'description',
            'is_activa',
        )

views.py

def add_discount(request, fair_pk, exhibitor_pk):
    fair = get_object_or_404(Fair, pk=fair_pk)
    exhibitor = get_object_or_404(
        Exhibitor, fair=fair, pk=exhibitor_pk, user=request.user)

    if request.method == 'GET':

        form = DiscountForm()

        return render(request, 'new_panel/add_discount.html', {
            'exhibitor': exhibitor,
            'discount_form': form,
        })

    if request.method == 'POST':
        form = DiscountForm(data=request.POST)

        if form.is_valid():
            discount = form.save(commit=False)
            discount.exhibitor = exhibitor
            discount.save()
            return redirect(reverse(
                'discounts_list',
                kwargs={"fair_pk": fair.pk, 'exhibitor_pk': exhibitor.pk}
            ))
        return render(request, 'new_panel/add_discount.html', {
            'exhibitor': exhibitor,
            'discount_form': form,
        })

第二种方法

我也尝试了不同的方法，使用单独的表单用于 POST，但它崩溃并出现相同的错误：

forms.py

class DiscountFormAdd(forms.ModelForm):

    class Meta:
        model = Discount
        fields = (
            'title',
            'exhibitor',
            'is_active',
        )

    def __init__(self, exhibitor, *args, **kwargs):
        self.exhibitor = exhibitor
        super(DiscountFormAdd, self).__init__(*args, **kwargs)

    def save(self, commit=False):
        discount = super(DiscountFormAdd, self).save(commit=False)
        discount.exhibitor = self.exhibitor

        if commit:
            discount.save()

        return discount

views.py

def add_discount(request, fair_pk, exhibitor_pk):
    fair = get_object_or_404(Fair, pk=fair_pk)
    exhibitor = get_object_or_404(
        Exhibitor, fair=fair, pk=exhibitor_pk, user=request.user)

    if request.method == 'GET':

        form = DiscountForm()

        return render(request, 'new_panel/add_discount.html', {
            'exhibitor': exhibitor,
            'discount_form': form,
        })

    if request.method == 'POST':
        form = DiscountFormAdd(data=request.POST, exhibitor=exhibitor)

        if form.is_valid():
            discount = form.save(commit=True)

            return redirect(reverse(
                'discounts_list',
                kwargs={"fair_pk": fair.pk, 'exhibitor_pk': exhibitor.pk}
            ))
        return render(request, 'new_panel/add_discount.html', {
            'exhibitor': exhibitor,
            'discount_form': form,
        })

我想坚持使用模型清理验证，而不是跳入清理表单。如果 django admin 能够做到，那么肯定可以在自定义模型表单中实现。

Answer 1

当使用self.exhibitor = exhibitor 指定参展商时，这会在您的表单上设置一个property，这与表单的内容无关。

要实际设置参展商，请改用以下代码：

import copy
.
.
.
    if request.method == 'POST':
        # request.POST is an immutable QueryDict so it needs to be copied
        form_data = copy.copy(request.POST)
        form_data['exhibitor'] = exhibitor.id
        form = DiscountFormAdd(data=form_data)

并完全放弃在表单的__init__ 中设置exhibitor

这样，您的表单数据（用于创建您的Discount）对象将是正确的并且可以被清理

[编辑] 如何在 ModelForm 中创建隐藏的输入字段：

class DiscountFormAdd(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(DiscountFormAdd, self).__init__(*args, **kwargs)
        self.fields['exhibitor'].widget = forms.HiddenInput()

    ...

或者你也可以使用 Meta 类的widgets 属性

class DiscountFormAdd(forms.ModelForm):

    class Meta:
        model = Discount
        widgets = {'exhibitor': forms.HiddenInput()}
        ...