如何在Django的Admin中检查FileField是否被修改？

Question

我正在尝试使用不应修改的文件创建一个模型。但文件的注释是可以的。

这是我所做的，但我们无法修改评论。 如何测试新文件（使用浏览按钮）是否已发送，并且仅在这种情况下创建模型的新实例？如果没有上传新文件，请更新评论。

admin.py

class CGUAdminForm(forms.ModelForm):
    class Meta:
        model = ConditionsUtilisation

    def clean_file(self):
        if self.instance and self.instance.pk is not None:
            raise forms.ValidationError(_(u'You cannot modify the file. Thank you to create a new instance.'))
        # do something that validates your data
        return self.cleaned_data["file"]

class CGUAdmin(admin.ModelAdmin):
    form = CGUAdminForm

admin.site.register(ConditionsUtilisation, CGUAdmin)

models.py

class ConditionsUtilisation(models.Model):
    date = models.DateField(_(u'Date d\'upload'), editable=False, auto_now_add=True)
    comment = models.TextField(_(u'Commentaire de modification'))
    file = models.FileField(_(u'CGU'), upload_to='subscription/cgu/', storage=CGUFileSystemStorage())

Answer 1

if 'file' in form.changed_data:
     """
     File is changed
     """
     raise forms.ValidationError("No, don't change the file because blah blah")
else:
     """
     File is not changed
     """