Get the list of related objects in django

Question

I have 3 models:

class Node(models.Model):
    ID = models.DecimalField(max_digits=19, decimal_places=10)
    name = models.CharField(default='node', max_length=32)
    connexion = models.CharField(max_length=255)
    # Many2one fields | Foreign keys:
    firm = models.ForeignKey('firme.Firme', on_delete=models.CASCADE, null=True, blank=True)


class ScheduledAction(models.Model):
    date = models.DateTimeField(default=datetime.now, blank=True)
    firm = models.ForeignKey('firme.Firme', on_delete=models.CASCADE, null=True, blank=True)
    node_ids = models.ManyToManyField(Node)

I want in ScheduledAction form to show, for a selected firm, the list of its related nodes. Normally I should do this by get:

class ScheduledActionForm(forms.ModelForm):
    date = forms.DateTimeField()
    firm = forms.ModelChoiceField(queryset=Firme.objects.all())
    node_ids = forms.ModelMultipleChoiceField(queryset=Node.objects.get(firm_id=firm.id), widget=forms.CheckboxSelectMultiple)

    class Meta:
        model = ScheduledAction
        fields = [
            'date',
            'firm',
            'node_ids'
        ]

This is my views.py:

def planification_view(request, id):
    scheduledAction = ScheduledActionForm(request.POST or None)
    firme = get_object_or_404(Firme, id=id)
    nodes = Node.objects.all()
    if scheduledAction.is_valid():
        scheduledAction.save()
        print('formulaire enregistre')
        scheduledAction = ScheduledActionForm()
    context = {
        'firme': firme,
        'form': scheduledAction,
        'nodes': nodes
    }
    return render(request, "node/planification.html", context)

But I got this error:

AttributeError: 'ModelChoiceField' object has no attribute 'id'

How can I fix this?

Matt · Accepted Answer · 2019-01-02 13:55:56Z

2

There are several things wrong with your approach

first of all: you assigned the variable 'firm' to a form field and then using that same variable to get an object from the db won't work in anyway. The variable 'firm' in Node.objects.get(firm_id=firm.id) should be a firm instance.

second: queryset=Node.objects.get(firm_id=firm.id) won't work because Model.objects.get() will return an object not a query set.

If you want to show all the nodes for a specific Firm you will need to pass the firm object (or id or other identifier) to the form by for example passing it through the get_form_kwargs() if you are using CBV and filtering by it Node.objects.filter(firm_id=firm.id)

Update: Since you are using function based views there might be a more dry way to do this, but I'm only used to working with CBV so I'll try my best

On the form we will declare a new variable called firme (we will pass this to the form in your view)

class ScheduledActionForm(forms.ModelForm):

def __init__(self, *args, **kwargs):
    self.firme = kwargs.pop('firme')
    super(ScheduledActionForm, self).__init__(*args, **kwargs)
    self.fields['node_ids'].queryset = Node.objects.filter(firm_id=self.firme.id)

date = forms.DateTimeField()
firm = forms.ModelChoiceField(queryset=Firme.objects.all()) # why do you want a list of all firms here? Or do you want a single object?
node_ids = forms.ModelMultipleChoiceField(queryset=Node.objects.none()), widget=forms.CheckboxSelectMultiple)

class Meta:
    model = ScheduledAction
    fields = [
        'date',
        'firm',
        'node_ids'
    ]

now for you view:

def planification_view(request, id):
firme = get_object_or_404(Firme, id=id)
nodes = Node.objects.all()
if request.method == 'POST':
    form = ScheduledActionForm(data=request.POST, firme=firme)
    if form.is_valid():
        scheduledAction = form.save()
        print('formulaire enregistre')
else:
    form = ScheduledActionForm(firme=firme)

context = {
    'firme': firme,
    'form': form,
    'nodes': nodes
}
return render(request, "node/planification.html", context)

Something along these lines should get you going. It might still require some tweaking to get it to work in your project. If you still have trouble understanding please read the Django docs and or do their tutorial

Update 2: Not the prettiest solution but it works for the OP

edited Jan 2, 2019 at 13:55

answered Jan 2, 2019 at 10:15

Matt

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6 Comments

Tessnim Over a year ago

I'm new to Django, can you please explain your solution in detail? Thanks.

Matt Over a year ago

can you show me the view you use to render the form?

Tessnim Over a year ago

I tried your code and got this error: NameError: name 'firme' is not defined

Matt Over a year ago

Sorry:

node_ids = forms.ModelMultipleChoiceField(queryset=Node.objects.filter(firm_id=firme.id), widget=forms.CheckboxSelectMultiple)

should be:

node_ids = forms.ModelMultipleChoiceField(queryset=Node.objects.filter(firm_id=self.firme.id), widget=forms.CheckboxSelectMultiple)

Tessnim Over a year ago

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