CODEWITHSUNDEEP
pythondjangopolymorphismdjango-queryset
Hugo Trentesaux
Hugo Trentesaux

Reputation: 1999

Filter by child class type

Lets say we have a class Place with a class Restaurant inheriting from it :

from django.db import models

class Place(models.Model):
    name = models.CharField(max_length=50)
    address = models.CharField(max_length=80)

class Restaurant(Place):
    serves_hot_dogs = models.BooleanField(default=False)
    serves_pizza = models.BooleanField(default=False)

If I have a class Tag related to places :

class Tag(models.Model):
    name = models.CharField(max_length=50)
    tagged = models.ManyToManyField(Place, related_name="tags")

For a given tag, how do I get a queryset selecting all Restaurants that have this tag, but not other kind of places ?

Upvotes: 2

Views: 255

Answers (1)

M.javid
M.javid

Reputation: 6647

The easiest way to doing this is calling filter from Restaurant.objects with something like :

Restaurant.objects.filter(tags=tag)

But if you want call filter from the Place.objects, you must use one of Django polymorphism apps such as Django-Polymorphic in your parent model because Django not supports models polymorphism by default.

Note: Read This article about OOP Polymorphism & This article for some extra information about Django model inheritance.

Upvotes: 1

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