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
17270	methods of the manager on subqueries QuerySet objects	Wojciech Banaś <fizista@…>	fizista@…	"Extends the operation methods of the manager on subqueries QuerySet objects.

The ""standard manager"" you can only like this:

{{{
SomeModel.object.some_method_manager().all().filter(...). ...
}}}


But this does not work:

{{{
SomeModel.object.all().some_method_manager()
}}}

And this it works with the use of this class / patches:

{{{
SomeModel.object.all().some_method_manager().filter(...).some_method_manager2(). ... 
SomeModel.object.some_method_manager().some_method_manager2().some_method_manager3(). ... 
}}}

Extension of the methods manager on all child objects ""QuerySeth"".

Example:

* class model
{{{
    class Animals(models.Model):
        type = models.CharField('Type of animal') # dog, cat, elephant
        color = models.CharField('Colour Name')
        
        objects = AnimalsManager()
}}}

* class manager

{{{
    class AnimalsManager(ManagerQuerySetDecorator):
    
        def get_dogs(self):
            return self.get_query_set().filter(type='dog')
        get_dogs.queryset_method = True
        
        def get_cats(self):
            return self.get_query_set().filter(type='cat')
        get_cats.queryset_method = True
        
        def get_white_animals(self):
            return self.get_query_set().filter(color='white')
        get_white_animals.queryset_method = True
        
        def get_black_animals(self):
            return self.get_query_set().filter(color='black')
        get_black_animals.queryset_method = True
        
        def get_brown_animals(self):
            return self.get_query_set().filter(color='black')

}}}

* add models data

{{{
    Animals(type='dog', color='black').save()
    Animals(type='dog', color='bown').save()
    Animals(type='dog', color='white').save()
    Animals(type='cat', color='black').save()
    Animals(type='cat', color='bown').save()
    Animals(type='cat', color='white').save()

}}}

* examples of actions a new manager

{{{
    animals = Animals.objects.get_black_animals().get_dogs()
    # return list black dogs

    animals = Animals.objects.get_white_animals().get_cats()
    # return list white cats
    
    # When ffff equals False, or not defined (as it is in 
    # the original model manager), we can not perform such an operation:
    animals = Animals.objects.get_cats().get_brown_animals()
    # return:
    # AttributeError: 'QuerySet' object has no attribute 'get_brown_animals'
    
    # but:
    animals = Animals.objects.get_brown_animals().get_cats()
    # return brown cats, because get_cat() present in all parent object instances.
}}}

In Annex file a class action extends the manager.

If there is interest in this patch, then add in the future full of tests, and prepare a ready-made patch for django code."	New feature	closed	Database layer (models, ORM)	dev	Normal	duplicate	queryset manager Extends	fizista@… 8mayday@…	Someday/Maybe	1	1	0	0	1	0