id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
16693	Unregistering ModelAdmin view and registering it again changing its contents is not realized when invoking it.	heidar_rafn	nobody	"When trying to make a change to the list_per_page option of a ModelAdmin class instance, 
it seems that the change is not activated on the fly. 
I first ""unregister"" the old ModelAdmin class and then ""register"" a new one (which is actually created)
but when trying to invoke the view, the old one is used, it looks like it is cached somewhere and the url-mechanism
is not using the re-created view, but invokes the old one.

After some investigation, I managed to create a work around that demonstrates what might be a bug,
see the code snippets, especially the ""changelist_view"" function - if it is omitted, 
the behavior I am describing happens.

Here are code snippets that demonstrate this:


{{{
# settings.py
...
FLIGHTADMININSTANCE = None
...
}}}




{{{
# myapp/admin.py
...
from django.conf import settings
from myapp.models import ConfigParameters
...
class FlightAdmin(admin.ModelAdmin):

    try:
        list_per_page = int(ConfigParameters.objects.get(name=""FLIGHTADMIN_LIST_PER_PAGE"").value)
    except:
        list_per_page = 5;
    ...

    def __init__(self, *args, **kwargs):
        super(FlightAdmin, self).__init__(*args, **kwargs)
        # store globally the object instance pointer
        settings.FLIGHTADMININSTANCE = self
        # following debug shows that the list_per_page is really changed
        print ""FlightAdmin created"", self, self.list_per_page

    def changelist_view(self, request, extra_context=None, **kwargs):
        # NOTE: following is to override some probably cached instance of the view 
        # and enables the changed view to be used instead of the first instance created
        # of the FlightAdmin class if this hook is not used
        return super(FlightAdmin, settings.FLIGHTADMININSTANCE).changelist_view(request, extra_context=extra_context)

...
admin.site.register(Flight, FlightAdmin)
...

def list_per_page_change(sender, instance, created, **kwargs):
    if instance.name == 'FLIGHTADMIN_LIST_PER_PAGE':
        # yes - the value is changing, change the FlightAdmin class accordingly
        admin.site.unregister(Flight)
        try:
            admin.site.register(Flight, FlightAdmin, list_per_page=int(instance.value))
        except:
            admin.site.register(Flight, FlightAdmin)

post_save.connect (list_per_page_change, sender=ConfigParameters)

}}}
"	Bug	closed	contrib.admin	1.3	Normal	invalid			Unreviewed	0	0	0	0	0	0