Sprequest.m is inherited from NSObject , its not a viewController subclass so you cant use
[self.navigationController pushViewController:dvrObj animated:YES];
внутри Sprequest.m
Вы можете получить объект navigationController из приложения appdelegate, например:
((AppDelegate *)[UIApplication sharedApplication].delegate).navigationController
затем используйте
[((AppDelegate *)[UIApplication sharedApplication].delegate).navigationController pushViewController:dvrObj animated:YES];