Django ModelForm with extra fields that are not in the model

Question

I have done a ModelForm adding some extra fields that are not in the model. I use these fields for some calcualtions when saving the form.

The extra fie

Answer 1

I had a very similar problem except it looked like I did all the required thing, but I was getting this error when Django was starting:

django.core.exceptions.FieldError: Unknown field(s) (my_new_field) specified for MyModel

This was a silly mistake from me, I accidentally declared my field using a Widget class:

class MyForm(forms.ModelForm):
    my_new_field = forms.HiddenInput()

Instead of a Field class:

class MyForm(forms.ModelForm):
    my_new_field = forms.CharField(widget=forms.HiddenInput())

Not answering the question at hand here (which is answered well already), but might help others.

Answer 2

In Django 2 you can just add the fields as it was a normal form

class CreateCompanyForm(forms.ModelForm):

    password_confirmation = forms.CharField(
        label=translate('Password confirmation'),
        max_length=70,
        widget=forms.PasswordInput(),
        required=True,
    )
    company_name = forms.CharField(
        label="Nombre de la Compañía",
        max_length=90,
        widget=forms.TextInput(),
        required=True,
    )

    class Meta:
        model = AppUser
        fields = (
            "email",
            "first_name",
            "last_name",
            "password",
        )

Answer 3

First, you shouldn't have artist_id and artist fields. They are build from the model. If you need some artist name, add artist_name field, that is CharField.

Furthermore, you are trying to retrieve something from cleaned_data inside clean value. There might not be data you need - you should use values from self.data, where is data directly from POST.

Answer 4

First add the field in the form

class CreateForm(forms.ModelForm):

extra_field     = forms.CharField(label = 'extra_field', required = False)

Now while cleaning you data, you need to retrive the extra field from self.data NOT self.cleaned_data

Correct:

 self.data.get('extra_field')

Wrong:

 self.cleaned_data.get('extra_field')

Answer 5

It's possible to extend Django ModelForm with extra fields. Imagine you have a custom User model and this ModelForm:

class ProfileForm(forms.ModelForm):

    class Meta:
        model = User
        fields = ['username', 'country', 'website', 'biography']

Now, imagine you want to include an extra field (not present in your User model, lets say an image avatar). Extend your form by doing this:

from django import forms

class AvatarProfileForm(ProfileForm):

    profile_avatar = forms.ImageField()

    class Meta(ProfileForm.Meta):
        fields = ProfileForm.Meta.fields + ('profile_avatar',)

Finally (given that the form has an ImageField), remember to include request.FILES when instantiating the form in your view:

# (view.py)

def edit_profile(request):
    ...
    form = AvatarProfileForm(
        request.POST or None, 
        request.FILES or None, 
        instance=request.user
    )
    ...

Hope it helps. Good luck!

EDIT:

I was getting a "can only concatenate tuple (not "list") to tuple" error in AvatarProfileForm.Meta.fields attribute. Changed it to a tuple and it worked.

Answer 6

This answer may be too late for the original poster, but I thought it might help others. I had the same problem and I did notice that self.cleaned_data('artist_id') can be accessed in the clean() method, but not in the clean_artist().

When I added the extra fields in the 'fields' declaration of Meta, then it worked.

    class Meta:
        model = Music
        fields=[..., 'artist_id']

You should be able to access the self.cleaned_data('artist_id') in clean_artist().