Django form inheritance not working init

Question

I have a form which I want all other forms to inherit from, below is what I have tried but I'm getting an error what suggests the init is not running from the AbstractFormBase class. SchemeForm 'should' inherit all the __init__ arguments before running its own.

Error:

'SchemeForm' object has no attribute 'fields'

Code Updated:

class AbstractFormBase(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        self.helper = FormHelper()
        self.helper.form_class = 'form-horizontal'
        self.helper.label_class = 'col-lg-3'
        self.helper.field_class = 'col-lg-8'

class SchemeForm(AbstractFormBase, NgModelFormMixin,):
    def __init__(self, *args, **kwargs):
        super(SchemeForm, self).__init__(*args, **kwargs)
        self.helper.layout = Layout(
            'name',
            'domain',
            'slug',

        )

Advanced Django Forms Usage pydanny/advanced-django-forms-usage is a valuable doc — fragles
– fragles, Commented Jan 10, 2014 at 11:09
Well, your form doesn't have any fields; a Django ModelForm requires either a fields or a exclude attribute on the Meta object. — Martijn Pieters
– Martijn Pieters, Commented Jan 10, 2014 at 11:16
Apart from that, your AbstractFormBase doesn't cooperate with any other classes in the inheritance structure. — Martijn Pieters
– Martijn Pieters, Commented Jan 10, 2014 at 11:18
@Martijn Pieters I see I need ModelForm on based form, however I don't want all forms to get the same model. guess I could do this with a function. — Prometheus
– Prometheus, Commented Jan 10, 2014 at 11:25

Martijn Pieters · Accepted Answer · 2018-09-28 11:09:50Z

Your AbstractFormBase class doesn't cooperate with the other classes in the inheritance tree. Your SchemeForm class has a specific MRO, a method resolution order. The super() call will only call the next __init__ method in that order, and AbstractFormBase is the next one (followed by NgModelFormMixin and forms.ModelForm).

You would want to pass on the __init__ call to the next class in the MRO by using super() in the AbstractFormBase class:

class AbstractFormBase(object):
    def __init__(self, *args, **kwargs):
        super(AbstractFormBase, self).__init__(*args, **kwargs)
        self.helper = FormHelper()
        self.helper.form_class = 'form-horizontal'
        self.helper.label_class = 'col-lg-3'
        self.helper.field_class = 'col-lg-8'

Note that the same applies to NgModelFormMixin, and that form.ModelForm requires that the Meta class has either a fields or a exclude attribute (see selecting the fields to use.)

ndpu · Accepted Answer · 2014-01-10 11:34:12Z

1

Place forms.ModelForm on first place in base classes list:

class SchemeForm(forms.ModelForm, AbstractFormBase, NgModelFormMixin):

and add object as AbstractFormBase base class and add super call in init:

class AbstractFormBase(object):
    def __init__(self, *args, **kwargs):
        super(AbstractFormBase, self).__init__(*args, **kwargs)

edited Jan 10, 2014 at 11:34

answered Jan 10, 2014 at 11:09

ndpu

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4 Comments

Prometheus Over a year ago

still not running :( 'SchemeForm' object has no attribute 'helper'

Martijn Pieters Over a year ago

No, object is not required here, but would be nice.

ndpu Over a year ago

@MartijnPieters and object is needed here, check your answer)

Martijn Pieters Over a year ago

@ndpu: no, not when the mixin is really used as a mixin. forms.ModelForm inherits (indirectly) from object already.

fragles · Accepted Answer · 2014-01-10 11:36:24Z

1

Your Base form needs to inherit from forms.ModelForm

see http://chriskief.com/2013/06/30/django-form-inheritance/

class AbstractFormBase(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        self.helper = FormHelper()
        self.helper.form_class = 'form-horizontal'
        self.helper.label_class = 'col-lg-3'
        self.helper.field_class = 'col-lg-8's

    class Meta:
        model = MyModel
        fields = ('field1', 'field2')

class SchemeForm(AbstractFormBase, NgModelFormMixin,):
    def __init__(self, *args, **kwargs):
        super(AbstractFormBase, self).__init__(*args, **kwargs)
            self.helper.layout = Layout(
            'name',
            'domain',
            'slug',
        )

    class Meta(AbstractFormBase.Meta):
        model = MyModel   # Or some other model
        fields = ('field3', 'field4')

edited Jan 10, 2014 at 11:36

answered Jan 10, 2014 at 11:16

fragles

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3 Comments

Prometheus Over a year ago

I have updated my OP based on your answer but I still get the same error, strange.

fragles Over a year ago

Try defining Meta and Fields

Martijn Pieters Over a year ago

Note that your version still should call the ModelForm init! Not calling super(AbstractFormBase, self).__init__(*args, **kwargs) will still break something.

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