Django ModelForm inheritance and Meta inheritance

问题

I have this ModelForm:

class Event(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super(Event, self).__init__(*args, **kwargs)
        ##Here make some changes such as:
        self.helper = FormHelper()
        self.helper.form_method = 'POST'
        ##Many settings here which **i don't want to rewrite in 10 child classes**

    class Meta:
        model = Event
        exclude = something...
        widgets = some settings here also.

And this child ModelForm:

class UpgradedEvent(Event):

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

    class Meta(Event.Meta):
        model = UpgradedEvent

UpgradedEvent is a child of Event model but has some extra fields. How can i inherit all the settings from the Event FORM into UpgradedEvent FORM?

When running the above code, it renders the Event form. Is there a way to inherit only the settings inside __init__ ?

EDIT

Check out the answer, it works great but keep in mind: you need to create another instance of FormHelper in your child class, otherwise it won't work. So child class should look something like:

class UpgradedEvent(Event):

    def __init__(self, *args, **kwargs):
        super(UpgradedEvent,self).__init__(*args,**kwargs)
        self.helper = FormHelper()

    class Meta(Event.Meta):
        model = UpgradedEvent

回答1:

Create FormWithSettings which will hold common settings for you form classes and inherit it

class FormWithSettings(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super(FormWithSettings, self).__init__(*args, **kwargs)
        ##Here make some changes such as:
        self.helper = FormHelper()
        self.helper.form_method = 'POST'
        ##Many settings here which **i don't want to rewrite in 10 child classes**

    class Meta:
        exclude = something...
        widgets = some settings here also.

class EventForm(FormWithSettings):

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

    class Meta(FormWithSettings.Meta):
        model = Event

class UpgradedEventForm(FormWithSettings):

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

    class Meta(FormWithSettings.Meta):
        model = UpgradedEvent

回答2:

You can obtain the fields the Meta above, and extend the lists, etc.:

class UpgradedEventForm(EventForm):

    def __init__(self, *args, **kwargs):
        super(UpgradedEventForm,self).__init__(*args,**kwargs)
        # some extra settings
        # ...
        # for example
        self.fields['extra_field'].initial = 'initial value of extra field'

    class Meta(EventForm.Meta):
        model = UpgradedEvent
        exclude = EventForm.Meta.exclude + ['extra_exclude1', 'extra_exclude2']
        fields = EventForm.Meta.fields + ['extra_field']

So by using inheritance, we can add extra procedures to the __init__ function by performing some extra actions after the super(UpgradedEventForm, self) call, and wwe can access the attributes of our parent, and extend these.

Note that you better name your forms with a Form suffix, since now your models clash with your forms. As a result, your Form seems to have as model a reference to the Form itself. By using proper "nomenclature", you avoid a lot of mistakes.

来源：https://stackoverflow.com/questions/50487334/django-modelform-inheritance-and-meta-inheritance

标签

python

django

inheritance

django-forms