[Django]-Dynamically update ModelForm's Meta class

by

59👍

✅

The Meta class is used to dynamically construct the form definition – so by the time you’ve created the ModelForm instance, the fields not in the exclude have already been added as the new object’s attributes.

The normal way to do it would be to just have multiple class definitions for each possible exclude list. But if you want the form itself to be dynamic, you’ll have to create a class definition on the fly. Something like:

def get_form(exclude_list):
    class MyForm(ModelForm):
        class Meta:
            model = Passenger
            exclude = exclude_list
    return MyForm

form_class = get_form(('field1', 'field2'))
form = form_class()

UPDATE: I just revisited this post and thought I’d post a little more idiomatic way to handle a dynamic class:

def PassengerForm(exclude_list, *args, **kwargs):
    class MyPassengerForm(ModelForm):
        class Meta:
            model = Passenger
            exclude = exclude_list

        def __init__(self):
            super(MyPassengerForm, self).__init__(*args, **kwargs)

    return MyPassengerForm()

form = PassengerForm(('field1', 'field2'))
👤Daniel Naab

13👍

Another way:

class PassengerInfoForm(ModelForm):
    def __init__(self, *args, **kwargs):
        exclude_list=kwargs.pop('exclude_list', '')

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

        for field in exclude_list:
            del self.fields[field]

    class Meta:
        model = Passenger

form = PassengerInfoForm(exclude_list=['field1', 'field2'])
👤user85461

4👍

Similar approach, somewhat different goal (generic ModelForm for arbitrary models):

from django.contrib.admin.widgets import AdminDateWidget
from django.forms import ModelForm
from django.db import models

def ModelFormFactory(some_model, *args, **kwargs):
    """
    Create a ModelForm for some_model
    """
    widdict = {}
    # set some widgets for special fields
    for field in some_model._meta.local_fields:
        if type(field) is models.DateField:
            widdict[field.name] = AdminDateWidget()

    class MyModelForm(ModelForm): # I use my personal BaseModelForm as parent
        class Meta:
            model = some_model
            widgets = widdict

    return MyModelForm(*args, **kwargs)
👤Hraban

3👍

Use modelform_factory (doc):

from django.forms.models import modelform_factory

from testprogram.online_bookings.models import Passenger

exclude = ('field1', 'field2')
CustomForm = modelform_factory(model=Passenger, exclude=exclude)  # generates ModelForm dynamically
custom_form = CustomForm(data=request.POST, ...)  # form instance
👤keisuke

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