Django get instance in inline form admin

Currently accepted solution is not thread safe. If you care about thread safety, never, ever assign an instance to a static class property.

Thread safe solutions are:

For Django 1.7 < 1.9 (possibly earlier versions, unclear):

from django.utils.functional import cached_property

def get_formset(self, *args, **kwargs):
    FormSet = super(InlineAdmin, self).get_formset(*args, **kwargs)

    class ProxyFormSet(FormSet):
        def __init__(self, *args, **kwargs):
            self.instance = kwargs['instance']
            super(ProxyFormSet, self).__init__(*args, **kwargs)

        @cached_property
        def forms(self):
            kwargs = {'instance': self.instance}
            forms = [self._construct_form(i, **kwargs) 
                    for i in xrange(self.total_form_count())]
            return forms
    return ProxyFormSet

As of Django >= 1.9 it's also possible to pass form_kwargs:

def get_formset(self, *args, **kwargs):
    FormSet = super(InlineAdmin, self).get_formset(*args, **kwargs)

    class ProxyFormSet(FormSet):
        def __init__(self, *args, **kwargs):
            form_kwargs = kwargs.pop('form_kwargs', {})
            form_kwargs['instance'] = kwargs['instance']
            super(ProxyFormSet, self).__init__(
                *args, form_kwargs=form_kwargs, **kwargs)
    return ProxyFormSet

Above solutions will make an instance kwarg available in the model form:

class InlineForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(InlineForm, self).__init__(*args, **kwargs)
        print('instance', kwargs['instance'])

Solution: Override the formset method in Inline class

def get_formset(self, request, obj=None, **kwargs):
        InlineForm.obj = obj
        return super(InlineAdmin, self).get_formset(request, obj, **kwargs)