如何从 Django DeleteView 发送错误消息？

假设有两个模型Parent and Child. Parent to child是一对多的关系。

我正在为父模型创建DeleteView。在删除之前我需要检查是否Parent has Children。如果没有Children then Parent模型照常删除。但如果有Children然后我需要将错误消息发送到DeleteView确认页面。

我如何使用DeleteView 来实现这一点？

DeleteView继承了删除混合 https://docs.djangoproject.com/en/2.1/ref/class-based-views/mixins-editing/#django.views.generic.edit.DeletionMixin。你能做的就是添加on_delete=PROTECTED在您的子模型中并覆盖视图中的删除方法以捕获ProtectedError例外。有关错误消息，请参阅 Django 的消息框架 https://docs.djangoproject.com/en/2.1/ref/contrib/messages/.

模型.py：

class Child():
    #...
    myParent = models.ForeignKey(Parent, on_delete=PROTECTED)

视图.py：

from django.db.models import ProtectedError

#...

class ParentDelete(DeleteView):
    #...
    def delete(self, request, *args, **kwargs):
        """
        Call the delete() method on the fetched object and then redirect to the
        success URL. If the object is protected, send an error message.
        """
        self.object = self.get_object()
        success_url = self.get_success_url()

        try:
            self.object.delete()
        except ProtectedError:
            messages.add_message(request, messages.ERROR, 'Can not delete: this parent has a child!')
            return # The url of the delete view (or whatever you want)

        return HttpResponseRedirect(success_url)