ManyToMany does not save to db Django

Question

I have a ManytoMany field and the results of the CheckboxSelectMultiple don't get saved in the db and i don't understand why. It must be really simple but...

Here's the code:

models.py

class Person(models.Model):

    last_name = models.CharField(max_length = 50)
    first_name = models.CharField(max_length = 50)

    def __str__(self):
        return self.last_name +" "+self.first_name

class Event(models.Model):
        owner = models.ForeignKey(User, on_delete=models.SET_NULL, null = True)
        person = models.ManyToManyField(Person)

forms.py

class EventForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        self.user = kwargs.get('user',None)
        #self.user = kwargs.pop('user',None)
        super(EventForm, self).__init__(*args, **kwargs)

        self.helper = FormHelper()
        self.helper.form_method = 'POST'
        #self.helper.form_action = reverse_lazy('simpleuser')
        self.helper.add_input(Submit('submit', 'Submit', css_class='btn-success'))     

    class Meta:
        model = Event
        fields = ['person']
        widgets ={
        'person': forms.CheckboxSelectMultiple,
        }

views.py

def uploadevent(request):

    if request.method == "POST":
        form =EventForm(request.POST)
        if form.is_valid():
            event = form.save(commit=False)
            event.owner = request.user
            event.save()
    else:
        form = EventForm()

    return render...

score 6 · Accepted Answer · answered May 17 '18 at 06:21

See the response on this stackoverflow question: Saving Many To Many data via a modelform in Django

Quoting the OP:

When using commit=False, you have to call save_m2m()

m2m relationships require the parent object to be saved first, which you are not doing by using commit=False

Just add this line below event.save()

    if form.is_valid():
        event = form.save(commit=False)
        event.owner = request.user
        event.save()
        form.save_m2m()

Ref: https://docs.djangoproject.com/en/2.0/topics/forms/modelforms/#the-save-method

score 0 · Answer 2 · answered May 17 '18 at 06:21

0

To save manytomany you should call save_m2m() when using commit=False (check details here):

if form.is_valid():
        event = form.save(commit=False)
        event.owner = request.user
        event.save()
        form.save_m2m()

answered May 17 '18 at 06:21

neverwalkaloner

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ManyToMany does not save to db Django

2 Answers2