InlineAdmin mixin limiting the selection of related items according to criteria which can depend on the current parent object being edited.

admin.py

class LimitedAdminInlineMixin(object):
    """
    InlineAdmin mixin limiting the selection of related items according to
    criteria which can depend on the current parent object being edited.

    A typical use case would be selecting a subset of related items from
    other inlines, ie. images, to have some relation to other inlines.

    Use as follows::

        class MyInline(LimitedAdminInlineMixin, admin.TabularInline):
            def get_filters(self, obj):
                return (('<field_name>', dict(<filters>)),)

    """

    @staticmethod
    def limit_inline_choices(formset, field, empty=False, **filters):
        """
        This function fetches the queryset with available choices for a given
        `field` and filters it based on the criteria specified in filters,
        unless `empty=True`. In this case, no choices will be made available.
        """
        assert formset.form.base_fields.has_key(field)

        qs = formset.form.base_fields[field].queryset
        if empty:
            logger.debug('Limiting the queryset to none')
            formset.form.base_fields[field].queryset = qs.none()
        else:
            qs = qs.filter(**filters)
            logger.debug('Limiting queryset for formset to: %s', qs)

            formset.form.base_fields[field].queryset = qs

    def get_formset(self, request, obj=None, **kwargs):
        """
        Make sure we can only select variations that relate to the current
        item.
        """
        formset = \
            super(LimitedAdminInlineMixin, self).get_formset(request,
                                                             obj,
                                                             **kwargs)

        for (field, filters) in self.get_filters(obj):
            if obj:
                self.limit_inline_choices(formset, field, **filters)
            else:
                self.limit_inline_choices(formset, field, empty=True)

        return formset

    def get_filters(self, obj):
        """
        Return filters for the specified fields. Filters should be in the
        following format::

            (('field_name', {'categories': obj}), ...)

        For this to work, we should either override `get_filters` in a
        subclass or define a `filters` property with the same syntax as this
        one.
        """
        return getattr(self, 'filters', ())

Thanks a lot. BTW, has_key is deprecated (i'm using Django >= 2.2) and if someone is getting error like:

AttributeError: 'collections.OrderedDict' object has no attribute 'has_key'

Just change Line-24:

assert formset.form.base_fields.has_key(field)

For:

assert field in formset.form.base_fields

Great tip! If you are perhaps able to make this a pull request (cllick the edit button on the file in question), I promise that it’ll be immediately accepted! :)

…

Op 10 mrt. 2020, om 12:27 heeft Alexandr Stefanitsky-Mozdor ***@***.***> het volgende geschreven: Thanks a lot. BTW, has_key is deprecated and if someone is getting error like: AttributeError: 'collections.OrderedDict' object has no attribute 'has_key' Just change Line-24 <https://gist.github.com/dokterbob/828117#file-admin-py-L24>: assert formset.form.base_fields.has_key(field) For: assert field in formset.form.base_fields — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://gist.github.com/828117?email_source=notifications&email_token=AAAFRVWC7I6LI3OFWDRUT33RGYW4TA5CNFSM4LE5ZCF2YY3PNVWWK3TUL52HS4DFVNDWS43UINXW23LFNZ2KUY3PNVWWK3TUL5UWJTQAGDXBG#gistcomment-3206675>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAFRVS3JH2T7GHWVL54MZTRGYW4TANCNFSM4LE5ZCFQ>.

Great tip! If you are perhaps able to make this a pull request (cllick the edit button on the file in question), I promise that it’ll be immediately accepted! :)

I dont think that is possible, but i created a fork.