如何在 Django 中查询多对多字段？

Question

我正在尝试更新一个视图，在给定当前登录用户的情况下，我拥有 return 我的宠物 table 的所有物品。我在 Pet 中有一个多对多字段 petowners.

PetOwner模型如下...

class PetOwner(models.Model):
    """Model representing a pet owner."""

    user = models.OneToOneField(User, on_delete=models.CASCADE)
    first_name = models.CharField(max_length=50, help_text="Enter owner's first name")
    last_name = models.CharField(max_length=50, help_text="Enter owner's last name")
    email = models.EmailField(
        max_length=50, blank=True, null=True, unique=True, help_text="Enter owner's email"
    )
    phone_number = models.CharField(
        max_length=15, blank=True, null=True, unique=True, help_text="Enter owner's phone number"
    )
    address = models.ForeignKey(
        "Address", on_delete=models.SET_NULL, null=True, blank=True
    )

Pet模型如下...

class Pet(models.Model):
    """Model representing a pet."""

    first_name = models.CharField(max_length=50, help_text="Enter pet's first name")
    last_name = models.CharField(max_length=50, help_text="Enter pet's last name")
    breeds = models.ManyToManyField("Breed", help_text="Select a breed for this pet")
    weight = models.DecimalField(
        max_digits=5, decimal_places=2, help_text="Enter pet's weight"
    )
    date_of_birth = models.DateField(null=True, blank=True)
    date_of_death = models.DateField("Died", null=True, blank=True)
    owners = models.ManyToManyField(PetOwner, help_text="Select an owner for this pet")
    address = models.ForeignKey(
        "Address", on_delete=models.SET_NULL, null=True, blank=True
    )

我正在使用 Django 已经提供给我们的 User 进行身份验证（注册和登录）。 PetOwner 是在用户创建他们的帐户时创建的，连同他们的名字和姓氏。 PetOwner 只有 email、phone_number 和 address 作为唯一字段，但不是必需的。因此，唯一性的保证来自 Django 的 User 模型中的 username。

我不想 return 我数据库中的所有宠物，而是我只想 return 当前登录用户的宠物。如下所示...

Pet.objects.filter(owners.contain(request.user))

也许通过使用用户名？我不知道如何写这个查询。

Answer 1

首先设置owners字段的related_name：

class Pet(models.Model):
    """Model representing a pet."""

    first_name = models.CharField(max_length=50, help_text="Enter pet's first name")
    last_name = models.CharField(max_length=50, help_text="Enter pet's last name")
    breeds = models.ManyToManyField("Breed", help_text="Select a breed for this pet")
    weight = models.DecimalField(
        max_digits=5, decimal_places=2, help_text="Enter pet's weight"
    )
    date_of_birth = models.DateField(null=True, blank=True)
    date_of_death = models.DateField("Died", null=True, blank=True)
    owners = models.ManyToManyField(PetOwner, help_text="Select an owner for this pet", related_name='pets')  # <- Here
    address = models.ForeignKey(
        "Address", on_delete=models.SET_NULL, null=True, blank=True
    )

那么你可以通过这个查询来获取用户的宠物：

target_user = User.objects.get(id=1)  # This is only an example
pet_owner = PetOwner.objects.get(user=target_user)
pets = pet_owner.pets.all()

如何在 Django 中查询多对多字段？

How to query many-to-many fields in Django?

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