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
In one of our recent projects, we had an interesting case: the whole application was built around an interactive map for a fairly large shopping mall, and the main goal of the system was to plot the closest route to a user-selected destination.
Once we received an interesting task from a client. They needed to allow their users to upload a 3D model of the building and show it in a timelapse video from the construction site.
In this article I’m going to show how to declare custom prosemirror node, how to render it with toDom method and how improve that with custom NodeView using React component.
Django ORM is a very abstract and flexible API. But if you do not know exactly how it works, you will likely end up with slow and heavy views, if you have not already. So, this article provides practical solutions to N+1 and high loading time issues. For clarity, I will create a simple view that demonstrates common ORM query problems and shows frequently used practices.
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.
In this beginners friends article I'll explain how to make authentication with Google account on your Django site and how to make authentication for you REST API.
