Django 表单视图：M 到 M 值未保存

Question

我的 Django 应用程序中有以下设置：

观看次数

class LearningObjectiveView( LoginRequiredMixin, FormView ):
  form_class = LearningObjectiveForm
  success_url = reverse_lazy( 'learning_objective' )
  template_name = 'learningobjective.html'

  def get_context_data( self, **kwargs ):
    trainee = Trainee.objects.get( username = self.request.user )
    context = super( LearningObjectiveView, self ).get_context_data( **kwargs )
    context['learningobjective'] = LearningObjective.objects.filter( trainee = trainee.id )
    context['topic'] = Topic.objects.filter( trainee = trainee.id )
    return context

  def form_valid( self, form ):
    self.object = form.save( commit = False )
    if self.request.user.is_authenticated():
      self.object.trainee = Trainee.objects.get( username = self.request.user )
    self.object.save()
    return super( LearningObjectiveView, self ).form_valid( form )

型号

class Topic( models.Model ):
  trainee = models.ForeignKey( Trainee )
  topic = models.TextField()

class LearningObjective( models.Model ):
  trainee = models.ForeignKey( Trainee )
  topic = models.ManyToManyField( Topic, blank = True, null = True )
  learning_objective = models.TextField()

表格

class LearningObjectiveForm( ModelForm ):
  class Meta:
    model = LearningObjective
    fields = ( 'learning_objective', 'topic', )

模板

{% extends "base.html" %}


{% block body %}

<table border="1">
 <th>Delete</th>
 <th>Lernziel</th>
 <th>Thema</th>
 {% for learningobj in learningobjective %}
  <tr>
   <td><a href="{% url 'learning_objective_delete' pk=learningobj.pk %}">Delete</a></td>
   <td>{{ learningobj.learning_objective }}</td>
   <td>{% for t in learningobj.topic.all %}{{ t.topic }}{% endfor %}</td>
  </tr>
 {% endfor %}
</table>

<form method="POST" action="{% url 'learning_objective_create' %}">
{% csrf_token %}
<table>
{{ form }}
</table>
<input type="submit" value="Speichern"/>
</form>

{% endblock %}

你们知道为什么这没有按预期工作吗？

当我提交我的表单时，我没有收到任何错误，只是创建了学习 objective 而不是主题。

编辑我现在对很多模型都使用这种方法。除多对多字段外，每个字段都有一个条目。提交表单时它们仍然为空。

我的一部分 self.request:

POST:<QueryDict: {u'topic': [u'2'], u'csrfmiddlewaretoken': [u'362xs1yPTk84nXencmqxuXkKKaq5ARKF'], u'learning_objective': [u'weq']}>,

由于这是一个查询集，我能否以某种方式获取它的值并将其保存在我的 FormView 中？真的没有人知道我该如何解决这个问题吗：/？

Answer 1

这里的代码似乎有点不正确，可以帮助您跟踪问题的几个更新是：

在您的 CreateModel 视图中定义：form_class = LearningObjectiveForm，模型 = LearningObjective
在您的模板中使用这里https://docs.djangoproject.com/en/1.7/topics/forms/#rendering-fields-manually提到的表格
再次从 CreateModel View 的 form_valid 方法中删除超级调用，因为这将再次调用 form.save()（可能会在此处创建重复对象）
我不确定我是否看到 RetrieveLearningObjective 视图的相关性。

Answer 2

这就是使用 commit=False 进行保存的方式，如 the documentation 中所述：

Another side effect of using commit=False is seen when your model has a many-to-many relation with another model. If your model has a many-to-many relation and you specify commit=False when you save a form, Django cannot immediately save the form data for the many-to-many relation. This is because it isn’t possible to save many-to-many data for an instance until the instance exists in the database.

To work around this problem, every time you save a form using commit=False, Django adds a save_m2m() method to your ModelForm subclass. After you’ve manually saved the instance produced by the form, you can invoke save_m2m() to save the many-to-many form data.

解决方案是调用 form.save_m2m()，这是在使用 commit=False.

调用表单的 save 方法时添加到表单实例的方法

def form_valid(self, form):
    self.object = form.save(commit=False)
    if self.request.user.is_authenticated():
        self.object.trainee = Trainee.objects.get(username=self.request.user)
    self.object.save()
    form.save_m2m()
    return super(LearningObjectiveView, self).form_valid(form)

Django 表单视图：M 到 M 值未保存

Django Form View: M to M values not saved

django

django-templates

django-forms

django-class-based-views