Add form fields to django form dynamically

Question

Due to a BD design where depending on a value, the data is stored in different cells, I have to add form fields dynamically. I was thinking on this:

class EditFlatForm(BaseModelForm):


    on_sale = forms.BooleanField(required=False)
    on_rent = forms.BooleanField(required=False)


    class Meta:

        model = Flat

        fields = ('title', 'flat_category', 'description')

        ...


    def __init__(self, *args, **kwargs):

        super(EditFlatForm, self).__init__(*args,**kwargs)


        flat_properties = FlatProperty.objects.all()

        for p in flat_properties:

            if p.type_value == 1:
                # Text
                setattr(self, p.title, forms.CharField(label=p.human_title, required=False))
            elif p.type_value == 2:
                # Number
                setattr(self, p.title, forms.IntegerField(label=p.human_title, required=False))
            else:
                # Boolean
                setattr(self, p.title, forms.BooleanField(label=p.human_title, required=False))

But the fields don't get added, what am I missing?

BaseModelForm is just a class I use to deal with labels, why shouldn't I use it? — Alfonso Embid-Desmet
– Alfonso Embid-Desmet, Commented Dec 16, 2014 at 12:05
perhaps self.fields[p.title] = forms....? assuming that p.title is a string — Mihai Zamfir
– Mihai Zamfir, Commented Dec 16, 2014 at 12:07
@MihaiZamfir omg, of course, what was I thinking, cheers mate, add it as a response and I'll accept it but I assume this question is going to be very redundant — Alfonso Embid-Desmet
– Alfonso Embid-Desmet, Commented Dec 16, 2014 at 12:11

Braiam · Accepted Answer · 2021-03-09 21:16:28Z

6

I recommend creating the form on the fly using type. So, you'll need to create a function that will generate a list of all the fields you want to have in your form and then use them to generate the form, something like this :

def get_form_class():
    flat_properties = FlatProperty.objects.all()
    form_fields = {}
    for p in flat_properties:
        if p.type_value == 1:
        form_fields['field_{0}'.format(p.id)] = django.forms.CharField(...)
        elif p.type_value == 2:
            form_fields['field_{0}'.format(p.id)] = django.forms.IntegerField(...)
        else:
            form_fields['field_{0}'.format(p.id)] = django.forms.BooleanField(...)
    # ok now form_fields has all the fields for our form
    return type('DynamicForm', (django.forms.Form,), form_fields  )

Now you can use get_form_class wherever you want to use your form, for instance

form_class = get_form_class()
form = form_class(request.GET) 
if form.is_valid() # etc

For more info, you can check my post on creating dynamic forms with django: http://spapas.github.io/2013/12/24/django-dynamic-forms/

Update to address OP's comment (But then how to gain advantage of all the things ModelForm provides?): You can inherit your dynamic form from ModelForm. Or, even better, you can create a class that is descendant of ModelForm and defines all the required methods and attributes (like clean, __init__, Meta etc). Then just inherit from that class by changing the type call to type('DynamicForm', (CustomForm,), form_fields ) !

edited Mar 9, 2021 at 21:16

Braiam

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answered Dec 16, 2014 at 12:51

Serafeim

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2 Comments

Alfonso Embid-Desmet Over a year ago

But then how to gain advantage of all the things ModelForm provides?

ArtOfWarfare Over a year ago

The dynamically created form ends up having a weird package name - if you try this str(type('PostForm2', (Form,), {})) - it returns <class 'django.forms.widgets.PostForm2'> - I feel like if the form is involved in an exception and shows up in a stacktrace, that'll really confuse people...

Mihai Zamfir · Accepted Answer · 2014-12-16 12:25:27Z

5

Assuming that p.title is a string variable, then this should work:

if p.type_value == 1:
     # Text
     self.fields[p.title] = forms.CharField(label=p.human_title, required=False))

answered Dec 16, 2014 at 12:25

Mihai Zamfir

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