It appears that not everyone knows that in python you can create classes dynamically without metaclasses. I'll show an example of how to do it.
So we've learned how to use custom QuerySet to chain requests:
Article.objects.old().public()Now we need to make it work for related objects:
user.articles.old().public()
This is done using use_for_related_fields, but it needs a little trick. Thing is that in django related managers are initialized without arguments, and our QuerySetManager takes argument - queryset class.
objects = QuerySetManager(MyQuerySet)We have to update QuerySetManager in such a way, that will allow setting queryset as class field:
class QuerySetManager(models.Manager):
use_for_related_fields = True
queryset_class = QuerySet
def get_query_set(self):
return self.queryset_class(self.model, using=self._db)
def __getattr__(self, key):
return getattr(self.get_query_set(), key)In order to use this manager, we have to create a sublcass and set queryset_class:
class MyManager(QuerySetManager):
queryset_class = MyQuerySetIt's not fun to create such class every time. So we'll write a function that does it for us:
def queryset_manager(qs_class):
class Manager(QuerySetManager):
queryset_class = qs_class
return Manager()Now it's enough to write:
objects = queryset_manager(MyQuerySet)Subscribe for the news and updates
This article explores Figma’s Dev Mode, a tool that streamlines design-to-code translation by enabling precise inspection, automated code generation, and seamless integration with design systems.
Promise is a powerful tool in asynchronous programming that allows developers to call a time-consuming function and proceed with program execution without waiting for the function result.
Designing database architecture is a challenging task, and it gets even more difficult when your app keeps getting bigger. Here are several tips on how to manage your data structure in a more efficient way.
Nowadays, when every second large company has developed its own instant messenger, in the era of iMessages, Slack, Hipchat, Messager, Google Allo, Zulip and others, I will tell you how to keep up with the trend and write your own chat, using django-channels 0.17.3, django 1.10.x, python 3.5.x.
Learn more about how to include jquery plugins in angular 2 running via webpack. Our tutorial is perfect for Angular beginners.
In this article, we will compare two most popular JS Libraries (Angular vs React). Both of them were created by professionals and have been used in famous big projects.