Django：通过从 ModelForm 中排除的字段进行验证

【问题标题】：Django: validate by field excluded from ModelFormDjango：通过从 ModelForm 中排除的字段进行验证
【发布时间】：2018-10-10 13:14:29
【问题描述】：

您可以通过将模型表单字段与排除字段进行比较来验证它吗？应该如何在init中设置excluded字段？

class MyModel(models.Model):
    amount = models.DecimalField()
    balance = models.DecimalField()

class MyForm(forms.ModelForm):
    def __init__(self, *args, **kwargs)
        self.balance = ??
        super(MyForm, self).__init__(*args, **kwargs)

    class Meta:
        model = MyModel
        fields = ['amount']

    def clean_amount(self):
        amount = self.cleaned_data['amount']
        if not (self.balance > 0 and amount > 0) or (self.balance < 0 and amount < 0):
            raise forms.ValidationError(
                'Cannot apply a negative amount to a positive balance and vice versa.')
        return amount

【问题讨论】：

标签： python django django-forms

【解决方案1】：

用您正在编辑的实例实例化表单：

instance = MyModel.objects.get(pk=pk)
form = MyForm(instance=instance, data=request.POST)

然后在表格中，您可以通过self.instance 访问余额。不需要在__init__ 方法中设置self.balance。

def clean_amount(self):
    amount = self.cleaned_data['amount']
    if not (self.instance.balance > 0 and amount > 0) or (self.instance.balance < 0 and amount < 0)
        raise forms.ValidationError(
            'Cannot apply a negative amount to a positive balance and vice versa.')
    return amount

【讨论】：