Display many to many relation relations in the template

Question

First of all I will post all the possibly necessary code. My models:

class topic(models.Model):
        learningObjectivesTopic = models.ManyToManyField(learningObjective, verbose_name = "Lernziel")
        topic = models.TextField(verbose_name = 'Thema')                         

class learningObjective(models.Model):
        learningObjectives = models.TextField(verbose_name = 'Lernziel')

My views:

@login_required(login_url='login')
def lernziel(request):
        return render(request, 'lernziel.html', {'topic': topic.objects.all(), 'todo': todoList.objects.all()})

@login_required(login_url='login')
def create_lernziel(request):
        neuesLernziel=learningObjective(learningObjectives=request.POST['Lernziel'])
        neuesLernziel.save()
        neuesLernziel_Topic=topic.objects.get(topic=request.POST['Thema'])
        neuesLernziel_Topic.learningObjectivesTopic.add(neuesLernziel)
        return render(request, 'lernziel.html', {'topic': topic.objects.all(), 'todo': todoList.objects.all()})

And the template I am using:

<html lang="{{ LANGUAGE_CODE|default:"de-de" }}" >
<head>
<h1 align = "center">Lernziele</h1>
</head>

<body>

<form action="{% url 'create_lernziel' %}" method="post">
{% csrf_token %}
<br>Hallo Benutzer: {{ user.username }}</br>
Lernziel: <textarea name="Lernziel" rows="3" cols="45" ></textarea>
<p>
 <select name="Thema" size="5">
  {% for topic_ in topic %}
   <option>{{ topic_.topic }}</option>
  {% endfor %}
 </select>
</p>
<input type="submit" value="Absenden" />
</form>

{% comment %}
Here should be the table which displays learning objectives and the related topics
{% endcomment %}

</body>
</html>

Ok I know my question is a bit weird because I don't have directly wrong code that I am posting. But I tried it so many times to display what I want properly but I just don't get how to do it right. My aim is to have 2 columns/headers: [learning objective] and [topics]. For every learning objective I want to have a new row. And in every row, it is possible to display more topics in relation. If you need more information or want me to be more specific about my problem please post it in the comments :)

Edit my first thought of that structure was that one: I iterate through the learning objectives, create a row for each one and and list the learning objectives and topics in that row then. Apparently it's not working. The Table probably has to be dynamic so that my idea is working or I just had a wrong thought.

<table border="1">
<th>Lernziel</th>
<th>Thema</th>

{% for topic_ in topic %}

        {% for lObj in topic_.learningObjectivesTopic.all %}
                <tr><td>{{ lObj }}</td>
        {% endfor %}

        <td>{{ topic_.topic }}</td></tr>

{% endfor %}

</table>

I'm not sure why you are still saving the neuesLernziel_Topic instance straight after you get it from the db - that seems to be left over from your previous version, but is pointless. — Daniel Roseman, Feb 26 '14 at 11:27

score 2 · Accepted Answer · edited Feb 26 '14 at 11:55

2

There isn't anything complicated here. You already know that you can get from an objective to its related topics by doing my_objective.topic_set.all(). So you just need to do that while you iterate through each topic in the template (and since it's a template, you drop the parentheses):

<table>
    {% for objective in objectives %}
    <tr>
      <td>{{ objective.learningObjectives }}</td>
      <td>{% for topic in objective.topic_set.all %}
             {{ topic.topic }}{% if forloop.last %},{% endif %}
          {% endfor %}</td>
    </tr>
    {% endfor %}
</table>

edited Feb 26 '14 at 11:55

BoJack Horseman

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answered Feb 26 '14 at 11:41

Daniel Roseman

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What are you confused about? The use of `topic_set.all`? Maybe [the docs](https://docs.djangoproject.com/en/1.6/topics/db/queries/#following-relationships-backward) on reverse relations will help you. – Daniel Roseman Feb 26 '14 at 11:56
how it works,see here: http://stackoverflow.com/questions/3748295/getting-the-sql-from-a-django-queryset – WeizhongTu Feb 26 '14 at 12:17

WeizhongTu · Answer 2 · 2014-02-26T11:48:09.697

models.py

class learningObjective(models.Model):
        learningObjectives = models.TextField(verbose_name = 'Lernziel')

class topic(models.Model):
        learningObjectivesTopic = models.ManyToManyField(learningObjective, verbose_name = "Lernziel")
        topic = models.TextField(verbose_name = 'Thema')

if you want to put topic ahead,use " or ',that is "learningObjective"

class topic(models.Model):
        learningObjectivesTopic = models.ManyToManyField("learningObjective", verbose_name = "Lernziel")
        topic = models.TextField(verbose_name = 'Thema')                         

class learningObjective(models.Model):
        learningObjectives = models.TextField(verbose_name = 'Lernziel')



<p>
 <select name="Thema" size="5">
  {% for topic_ in topic %}
   <option>{{ topic_.topic }}</option>
   {% for lo in topic_.learningObjectivesTopic.all %}
        <option>{{ lo.learningObjectives }}</option>
   {% endfor %}
  {% endfor %}
 </select>
</p>

If you want to get topic from learningObjective

lo = learningObjective.objects.all()[0]
lo.topic_set()

in templates,remove "()", I believe that you know how to use it in templates.

Display many to many relation relations in the template

2 Answers2