CODEWITHSUNDEEP
pythondjangodjango-modelsdjango-viewsdjango-templates
HBMCS
HBMCS

Reputation: 776

Accessing many-to-many details with through model in Django template

I have a models.py like this:

class Work(models.Model):
[...]
    instrumentations = models.ManyToManyField('Instrument', 'Percussion',
        through='Instrumentation',
        blank=True)

class Instrument(models.Model):
    name = models.CharField(max_length=100)
    family = models.CharField(max_length=20, default='')

class Percussion(models.Model):
    name = models.CharField(max_length=100)

class Instrumentation(models.Model):

    players = models.IntegerField()
    work = models.ForeignKey(Work, on_delete=models.CASCADE)
    instrument = models.ForeignKey(Instrument, on_delete=models.CASCADE)
    percussion = models.ManyToManyField(Percussion, blank=True, default=None) # Ideally percussions should be in the Instrument model with family 'percussion', though I don't know how to make Django like that. A separate model is a good workaround for me.

My view:

def work_edit_view(request, id=id):

    InstrumentFormSet = inlineformset_factory(Work, Work.instrumentations.through, extra=1, can_delete=True,
    fields=('instrument', 'percussion', 'players', 'work'), widgets={
    'work': forms.HiddenInput(),
    'players': forms.NumberInput(attrs={'placeholder': 'Number of players'})
    form_details = InstrumentFormSet(request.POST or None, instance=obj_work, initial=[{'work' : obj_work.id}], prefix='instruments')

})

The data gets saved correctly in my input form, so that's not an issue. My problem is visualising the information in my template. I can only access the 'instrument', not my 'percussion' or my 'players'. What am I doing wrong?

    {% for instrument in work.instrumentations.all %}
    {{ instrument }} {{ instrument.players }} # only instrument is output.

      {% for percussion in instrument.percussion.all %} # this looks to be empty.
      Percussion {{ forloop.counter }} ({{ percussion.players }}) # No luck here :(
      {% endfor %}

Upvotes: 1

Views: 171

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477180

You can, but you need to access it correctly, you can access the Instrumentations with work.instrumentation_set:

{% for instrumentation in work.instrumentation_set.all %}
    {{ instrumentation.instrument }} {{ instrumentation.players }}

    {% for percussion in instrumentation.percussion.all %}
        Percussion {{ forloop.counter }} ({{ percussion.players }})
    {% endfor %}
{% endfor %}

Note: that a ManyToManyField can not refer to multiple models. The second parameter is the related_name, so you set the name of the relation in reverse to 'Percussion', which might not be ideal.

Upvotes: 1

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