Add and initialize custom field in Django ModelForm

Question

I feel like I am missing some very basic point, but can't solve this.
Let's say I have model like this one:

class Person(models.Model):
    first_name = models.CharField(max_length=256, blank=True)
    # this is weird field, but needed for my usecase
    last_name = models.WeirdCustomField(max_length=256, blank=True)

And there is a form for this, which I would like to customize a bit (comments):

class PersonForm(forms.ModelForm):

    class Meta:
        model = Address
        # I want to override 'last_name' field, so exclude it here
        exclude = ['last_name']

    # And add additional field
    my_field = ChoiceField(choices=list_of_choicec)
    last_name = forms.CharField()

    def __init__(self, *args, **kwargs):
        last_name = kwargs.pop('last_name', None)
        my_field = kwargs.pop('my_field', None)
        super(PersonForm, self).__init__(*args, **kwargs)
        self.fields['last_name'] = last_name
        self.fields['my_field'] = my_field

Now, in the shell (after all imports...)

person = Person.objects.get(first_name='Jacob')
person.first_name # Prints 'Jacob', correct!
form = PersonForm(instance=person, last_name='Smith', my_field='test123')
form['first_name'].value() # -> 'Jacob', that's right
form['last_name'].value() # -> nothing, I expected 'Smith'
form['my_field'].value() # -> nothing, I would like to see 'test123'

I think I dig Internet very deep, but could not find solutions for this kind of problem.

Sandeep Balagopal · Accepted Answer · 2017-12-01 12:33:48Z

7

You have to set the initial value. In your init try replace with below code.

self.fields['last_name'].initial = last_name
self.fields['my_field'].initial = my_field

The initial can also be passed when the form instance is created.

form = PersonForm(instance=person, initial={'last_name'='Smith', 'my_field'='test123'})

This one is the recommended way to do it. Don't have to override the init method at all.

edited Dec 1, 2017 at 12:33

answered Dec 1, 2017 at 12:14

Sandeep Balagopal

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4 Comments

Photon Light Over a year ago

Amazing, I don't think I would figure it out myself in the near future, thank you! I also need to say, it is quite counter intuitive, but I guess it's the framework way.

Sandeep Balagopal Over a year ago

try printing self.fields['my_field'] in your init. You can see what it is.

rammanoj Over a year ago

how to perform this in generic views ??

Sandeep Balagopal Over a year ago

Which generic view are you using ?

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