Django - Admin - Inline - 'extra' value based on some condition

Question

Is it possible to dynamically set the 'extra' option in the Django Admin Inline?

For example, If Student class have Address class as Inline. If there is no Address inline's associated with Student, then extra =1. If there is any Address inline's associated with Student, then extra =0.

Answer 1

Just simply override the get_extra method. The following example set extra to 0 for the add view and 10 for the edit view.

class MyInline(admin.TabularInline):
    model = MyModel

    def get_extra(self, request, obj=None, **kwargs):
        return 0 if obj else 10

Answer 2

You can just leverage inheritance..

// based on some condition
kwargs['extra'] = something
.........
return super(*******Inline, self).get_formset(request, obj, **kwargs) // 'defaults.update(kwargs)' takes care of the dynamic overriding 

The get_formset method from my project :

def get_formset(self, request, obj=None, **kwargs):
    ## Put in your condition here and assign extra accordingly
    if obj is None:
        return super(ImageInline, self).get_formset(request, obj, **kwargs)
    current_topic = TopicPage.objects.get(pk = obj.id)
    topic_images = ThruImage.objects.filter(topic = current_topic)

    kwargs['extra'] = 0
    if len(topic_images) <= 3:
        kwargs['extra'] = 3 - len(topic_images)
    return super(ImageInline, self).get_formset(request, obj, **kwargs)

This is of course, useful only for simple conditionals based off the parent model object ..