#25408: Pass additional arguments to BaseForm.__init__ from
BaseModelForm.__init__
-------------------------------------+-------------------------------------
Reporter: MoritzS | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Forms | Version: master
Severity: Normal | Resolution:
Keywords: form modelform args | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by MoritzS):
The reason you need to inherit it from `BaseForm` becomes more obvious
when you look at the mro of the forms. Suppose you have a `UserForm`.
Normally its mro will look like this:
{{{
UserForm
django.forms.forms.BaseForm
object
}}}
Now you want to add functionality to all forms in your project so you
create a new mixin called `ProjectFormMixin`. If you then have a new
`MyProjectBaseForm` like this:
{{{
class MyProjectBaseForm(ProjectFormMixin, BaseForm):
def has_changed(self):
# custom detection if form has changed that also calls
# super().has_changed() at some point
}}}
And `UserForm`'s mro (if you inherit it from `MyProjectBaseForm`) will now
be:
{{{
UserForm
MyProjectBaseForm
ProjectFormMixin
django.forms.forms.BaseForm
object
}}}
However if you also want to use this mixin in a model form base like this:
{{{
class MyProjectBaseModelForm(ProjectFormMixin, BaseModelForm):
pass
}}}
the mro of a `UserModelForm` will be:
{{{
UserModelForm
MyProjectBaseModelForm
ProjectFormMixin
django.forms.models.BaseModelForm
django.forms.forms.BaseForm
object
}}}
when instead you wanted `ProjectFormMixin` to be right above
`django.forms.forms.BaseForm`.
That's because `super()` calls inside the `ProjectFormMixin` will then hit
`BaseForm` as intended instead of `BaseModelForm`.
Also `super()` calls form within `BaseModelForm` (they only relevant one
is in `BaseModelForm.__init__()`) will then hit your `ProjectFormMixin`
instead of the other way around.
--
Ticket URL: <https://code.djangoproject.com/ticket/25408#comment:2>
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