试图在 STUDENT 模型（外键）中保存 POST 数据 CLASS NAME？

Question

我正在尝试在页面上以表单形式显示类。当点击注册按钮时，我得到班级名称并将其分配给学生模型（它具有班级模型的外键）..

更新：

新错误：/enrol/ 处的 ValueError 无法分配“'guitar101'”：“StudentProfile.student_class”必须是“MusicClass”实例。

• django 新手，我不知道自己在做什么，请帮忙！ 我的尝试，有什么问题？

models.py

class StudentProfile(models.Model):
    user = models.OneToOneField('Accounts', related_name='student_profile')
    student_class = models.ForeignKey(to=MusicClass, related_name="student_class", null=True, blank=True)
    is_student = models.BooleanField('student status', default=True)
     # more fields


class MusicClass(models.Model):
    class_name = models.CharField(max_length=500, blank=True)
    # more fields 

views.py

# enrolls student
def studentEnrol(request):

    if request.method == "POST":
       musicClass     = request.POST.get('musicClass', '')
       student_profile  = StudentProfile(student_class=musicClass)
       student_profile.save()
       return HttpResponseRedirect('/') 


    else:    
        querySet = MusicClass.objects.all()
        args = {'classes': querySet }

    return render(request, 'accounts/enrol.html', args)

forms.py

class MusicClassesEnrolForm(forms.ModelForm):
    class Meta:
        model = MusicClass
        fields = ('class_name', 'class_level', 'class_time', 'class_room', 'instrument_taught', 'day', 'teacher')

enrol.html

 {% extends 'base.html' %}

 {% block body %}
 <div class="outer"><div class="container">
     <h1> Enrol into Class </h1>

    <table style="width:100%">
      <tr>
        <th>Class Name</th>
        <th>Instrument</th> 
        <th>Class Level</th>
        <th>Time</th>
        <th>Teacher</th>
        <th>Room</th>
        <th>Register</th>
      </tr><br>
        {% for class in classes %}

          <tr>
            <td>{{ class.class_name }}</td>
            <td>{{ class.instrument_taught }}</td>
            <td>{{ class.class_level }}</td>
            <td>{{ class.class_time }}</td>
            <td>{{ class.teacher }}</td>
            <td>{{ class.class_room }}</td>
            <td><form method="post">
                {% csrf_token %}
                <input type="hidden" name="musicClass" value="{{ class.class_name }}">
                <input type="submit" name="enrolBtn" value="Enrol">
            </form></td>
          </tr>

        {% endfor %}
     <table>


    </p>

</div>
</div>
{% include "footer.html" %}
{% endblock %}

请出主意？

更新 - 添加追溯

Environment:


Request Method: POST
Request URL: http://127.0.0.1:8000/enrol/

Django Version: 1.11.7
Python Version: 3.6.5
Installed Applications:
['accounts',
 'timetable',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "C:\Users\N9587268\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\handlers\exception.py" in inner
  41.             response = get_response(request)

File "C:\Users\N9587268\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\handlers\base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "C:\Users\N9587268\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\handlers\base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "D:\ifb299\webrepo\musicwebsite\website\accounts\views.py" in studentEnrol
  127.        StudentProfile = StudentProfile(student_class=musicClass)

Exception Type: UnboundLocalError at /enrol/
Exception Value: local variable 'StudentProfile' referenced before assignment

请求信息 POST（例如，这是我在点击注册 btn 时从帖子中获得的信息）

csrfmiddlewaretoken 
'TY28RiLjhtu98v8uthXFuCGJ4pPO3z6e02IDa6x8UFujenzEZdECunhxuqcAKtCw'
musicClass  
'guitar101'
enrolBtn    
'Enrol'

Answer 1

现在您尝试将 string 分配给不正确的 ForeignKey 字段。 获得musicClass = request.POST.get('musicClass', '') 后，您应该拥有或创建一个MusicClass 实例

我用get_or_create

# @login_required # A login decorator is very important here
def studentEnrol(request):
    user = request.user
    if not hasattr(user,'student_profile'): 
         # The current user doesn't have student_profile attribute
         # redirect to the page you want
         return redirect('completeProfile') # for instance
    student_profile = request.user.student_profile
    if request.method == "POST":
         id_musicClass     = request.POST.get('musicClass')
         music_class = MusicClass.objects.get(id=id_musicClass)
         # or music_class = get_object_or_404(MusicClass,id=id_musicClass)
         student_profile.student_class = music_class
         student_profile.save()
         return HttpResponseRedirect('/') 
    else:
        '''rest of the codes'''

Answer 2

musicClass 变量包含MusicClass 对象的id，而不是实例本身：

musicClass     = request.POST.get('musicClass', '')
student_profile  = StudentProfile(student_class=musicClass)

为了将其分配给student_class 字段，您需要该实例。试试这个：

music_class_id = int(request.POST.get('musicClass'))
music_class = MusicClass.objects.get(pk=music_class_id)
student_profile  = StudentProfile(student_class=music_class)

并更改以下行

<input type="hidden" name="musicClass" value="{{ class.class_name }}">

到

<input type="hidden" name="musicClass" value="{{ class.id }}">