Django CreateView：如何在保存时执行操作 [英] Django CreateView: How to perform action upon save

问题描述

我正在使用自定义的CreateView（CourseCreate）和UpdateView（CourseUpdate）保存和更新课程。保存课程后，我想采取措施。我将在新课程的讲师和用户之间建立新的多对多关系（如果尚不存在）。

I'm using a custom CreateView (CourseCreate) and UpdateView (CourseUpdate) to save and update a Course. I want to take an action when the Course is saved. I will create a new many-to-many relationship between the instructor of the new course and the user (if it doesn't already exist).

因此，我想将课程另存为课程，然后使用course.faculty创建新关系。做到这一点的最佳地点在哪里？

So, I want to save the Course as course, and then use course.faculty to create that new relationship. Where is the best place to make this happen?

我试图在视图中的form_valid中执行此操作，但是在尝试访问form.instance.faculty bc时出现错误，未创建课程还没有（在CourseCreate中）。错误消息如下：

I'm trying to do this in form_valid in the views, but I'm getting errors when trying to access form.instance.faculty bc the course isn't created yet (in CourseCreate). The error message is like:

课程：...必须具有字段 course的值，然后才能使用这种多对多关系。

"Course: ..." needs to have a value for field "course" before this many-to-many relationship can be used.

它在CourseUpdate中也不起作用。助手关系未创建。我应该在表格中尝试吗？但是我不确定如何将用户信息发送到表单。
谢谢。

It's also not working in CourseUpdate. The Assists relationship is not created. Should I be trying this in the Form? But I'm not sure how to get the user info to the Form. Thank you.

models.py

models.py

class Faculty(models.Model):
    last_name = models.CharField(max_length=20)

class Course(models.Model):
    class_title = models.CharField(max_length=120)
    faculty = models.ManyToManyField(Faculty)

class UserProfile(models.Model):
    user = models.OneToOneField(User)
    faculty = models.ManyToManyField(Faculty, through='Assists')

class Assists(models.Model):
    user = models.ForeignKey(UserProfile)
    faculty = models.ForeignKey(Faculty)

views.py

class CourseCreate(CreateView):
    model = Course
    template_name = 'mcadb/course_form.html'
    form_class = CourseForm
    def form_valid(self, form):
        my_course = form.instance
        for f in my_course.faculty.all():
            a, created = Assists.objects.get_or_create(user=self.request.user.userprofile, faculty=f)
        return super(CourseCreate, self).form_valid(form)

class CourseUpdate(UpdateView):
    model = Course
    form_class = CourseForm
    def form_valid(self, form):
        my_course = form.instance
        for f in my_course.faculty.all():
            a, created = Assists.objects.get_or_create(user=self.request.user.userprofile, faculty=f)
        return super(CourseUpdate, self).form_valid(form)

推荐答案

form_valid（） 方法用于 CreateView 和 UpdateView 保存表单，然后重定向到成功URL。 返回super（）是不可能的，因为要在被保存的对象和重定向之间进行操作。

The form_valid() method for CreateView and UpdateView saves the form, then redirects to the success url. It's not possible to do return super(), because you want to do stuff in between the object being saved and the redirect.

第一个选择是不调用 super（），并在视图中复制两行。这样做的好处是非常清楚发生了什么。

The first option is to not call super(), and duplicate the two lines in your view. The advantage of this is that it's very clear what is going on.

def form_valid(self, form):
    self.object = form.save()
    # do something with self.object
    # remember the import: from django.http import HttpResponseRedirect
    return HttpResponseRedirect(self.get_success_url())

第二种选择是继续调用 super（），但在更新关系之前，不要返回响应。这样做的好处是您没有复制 super（）中的代码，但是缺点是不清楚所发生的事情，除非您熟悉 super（）。

The second option is to continue to call super(), but don't return the response until after you have updated the relationship. The advantage of this is that you are not duplicating the code in super(), but the disadvantage is that it's not as clear what's going on, unless you are familiar with what super() does.

def form_valid(self, form):
    response = super(CourseCreate, self).form_valid(form)
    # do something with self.object
    return response

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