Django - Model field keeps the same value!

When I assign a value to an variable of a Field object, why when I reload the ModelForm isn't reassigned to default?

File

class CustomFile(ImageFile, FieldFile):
    def save(self, name, content, save = True):
        if self.field.override_name:
            self(CustomFile, self).save(self.field.override_name, content, save = save)
        else:
            self(CustomFile, self).save(generate_name(self.instance, name), content, save = save)

Field

class CustomImageField(ImageField):
    attr_class = CustomFile
    def __init__(self, overrided_name, *args, **kwargs):
        self.overrided_name = overrided_name
        super(CustomImageField, self).__init__(*args, **kwargs)

Model

class Test(models.Model):
    email = models.EmailField()
    file = CustomImageField()

AdminForm

class TestForm(ModelForm):
    def __init__(self, *args, **kwargs):
        super(TestForm, self).__init__(*args, **kwargs)
        self.old_instance = self.instance

Admin

class TestAdmin(Test):
    form = TestForm

    def save_model(self, request, obj, form, change):
        if form.old_instance:
            form.old_instance.file.delete(save = True)
            form.old_instance.file.field.override_name = form.old_instance.name
        obj.save()

admin.site.register(Test, TestAdmin)

My problem is that every image I will upload will have the same name, until I restart the server!.. Why the object doesn't change?! In particular the Field object... when I trace it will result the same object .

I've solved it like so:

class CustomFile(ImageFile, FieldFile):
    def save(self, name, content, save = True):
        if self.field.override_name:
            self(CustomFile, self).save(sel开发者_如何学编程f.field.override_name, content, save = save)
            self.field.override_name = None
        else:
            self(CustomFile, self).save(generate_name(self.instance, name), content, save = save)

I'm using Django 1.2.6, Python 2.6 and Windows!

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I am just guessing, but isnt this part of code wrong?

form = TestForm

Should not it be creating an instance instead of referencing to class?

form = TestForm()

or same thing here?

attr_class = CustomFile  - > attr_class = CustomFile()