from django.contrib.admin.util import unquote
from django.db import models as django_models
import os 

class CustomModelAdmin(admin.ModelAdmin):
    def change_view(self, request, object_id, extra_context=None):
        #Original ImageField attr's
        obj = self.get_object(request, unquote(object_id))
        for field in obj._meta.fields:
            if (isinstance(field, django_models.ImageField) or isinstance(field, django_models.FileField))\
                    and request.FILES.has_key(field.name):
                setattr(obj, 'old_%s'%(field.name), getattr(obj, field.name)) 
                
        ModelForm = self.get_form(request, obj)
        if request.method == 'POST':
            form = ModelForm(request.POST, request.FILES, instance=obj)
            if form.is_valid():
                for field in obj._meta.fields:
                    #Overwriting ImageField attr's
                    if (isinstance(field, django_models.ImageField) or isinstance(field, django_models.FileField))\
                            and request.FILES.has_key(field.name):
                        path = getattr(obj, 'old_%s'%(field.name))
                        if path and os.path.isfile(path.path):
                            os.unlink(path.path)

        return super(CustomModelAdmin, self).change_view(request, object_id, extra_context=extra_context)