objective c - applicationWillTerminate does not get invoked -

i want save data before terminating, appcontroll class conforms nsapplicationdelegate protocol, , declared method; , in interface builder bound window's delegate outlet appcontroller, cannot method invoked.

where wrong, should do?

did remember add handler application?

uiapplication *app = [uiapplication sharedapplication]; [[nsnotificationcenter defaultcenter]     addobserver:self    selector:@selector(applicationwillterminate:)    name:uiapplicationwillterminatenotification object:app];