Get models ordered by an attribute that belongs to its OneToOne model
django, python, python-3.x
Solution
Use the double-underscore syntax.
User.objects.order_by('-pet__age')[:10]
Edit
To get the ten friends of Tom, you can get the instance and filter:
User.objects.get(name='Tom').friends.order_by('-pet__age')[:10]
or if you already have Tom:
tom.friends.order_by('-pet__age')[:10]
Problem
Let's say there is one model named `User` and the other named `Pet` which has a `OneToOne` relationship with `User`, the `Pet` model has an attribute `age`, how to get the ten `User` that owns the top ten `oldest` dog? ``` class User(models.Model): name = models.CharField(max_length=50, null=False, blank=False) class Pet(models.Model): name = models.CharField(max_length=50, null=False, blank=False) owner = models.OneToOneField(User, on_delete=models.CASCADE) age = models.IntegerField(null=False) ``` In `User`, there is an attribute `friends` that has a `ManyToMany` relationship with `User`, how to get the ten `friends` of `User Tom` that owns the top ten `oldest` dog? ``` class User(models.Model): name = models.CharField(max_length=50, null=False, blank=False) friends = models.ManyToManyField(self, ...) class Pet(models.Model): name = models.CharField(max_length=50, null=False, blank=False) owner = models.OneToOneField(User, on_delete=models.CASCADE) age = models.IntegerField(null=False) ```