Question

我与用户和公司之间存在多对一外键关系。为了将用户添加到公司，我需要使用反向关系。每个公司都有许多用户。使用python shell，我可以通过以下方式将现有用户添加到公司中：

company.user_set.add（用户）

我对如何在序列化器上执行相同的操作感到困惑。我能够修补用户列表，它将保存关系，但是我想追加一个用户，而不是每次都覆盖所有用户。我看到了一些建议，例如获取当前用户列表并追加新用户，然后保存新列表。我不知道如何实现该功能。

class Company(models.Model):

    company_name = models.CharField(max_length=255)
    address = models.CharField(max_length=255)
    state = models.CharField(max_length=255)
    city = models.CharField(max_length=255)

class User(AbstractBaseUser):

    email = models.EmailField(max_length=255, unique=True)
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

    USERNAME_FIELD = 'email'

    is_admin = models.BooleanField(default=False)
    is_active = models.BooleanField(default=True)
    company = models.ForeignKey(Company, on_delete=models.CASCADE, null=True)

    objects = UserManager()


class CompanyUpdateSerializer(serializers.ModelSerializer):

    user_set = UserSerializer(many=True)

    class Meta:
        model = Company
        fields = ('company_name', 'user_set',)

    def to_internal_value(self, data):
        self.fields['user_set'] = serializers.SlugRelatedField(
            queryset=User.objects.all(), many=True, slug_field='email')
        return super(CompanyUpdateSerializer, self).to_internal_value(data)

Answer 1

您可以通过这种方式进行。在您的序列化器中：

Operations to perform:
  Apply all migrations: Blog, Portfolio, admin, auth, contenttypes, sessions
Running migrations:
  Applying Blog.0002_auto_20180728_0218...Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\commands\migrate.py", line 200, in handle
    fake_initial=fake_initial,
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\migration.py", line 122, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\operations\fields.py", line 216, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 525, in alter_field
    old_db_params, new_db_params, strict)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\postgresql\schema.py", line 122, in _alter_field
    new_db_params, strict,
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 629, in _alter_field
    old_default = self.effective_default(old_field)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 240, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 767, in get_db_prep_save
    return self.get_db_prep_value(value, connection=connection, prepared=False)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1276, in get_db_prep_value
    value = self.get_prep_value(value)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1271, in get_prep_value
    return self.to_python(value)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1246, in to_python
    params={'value': value},
django.core.exceptions.ValidationError: ["'' value has an invalid date format. It must be in YYYY-MM-DD format."]

现在，您通过以下方式执行PATCH请求：

class CompanyUpdateSerializer(serializers.ModelSerializer):

    users = serializers.PrimaryKeyRelatedField(many=True, queryset=User.objects.all(), write_only=True)

    user_set = UserSerializer(many=True, read_only=True)

    class Meta:
        model = Company
        fields = ('company_name', 'user_set', 'users')

    def update(self, instance, validated_data):

        users = validated_data.pop('users', None)

        instance = super().update(instance, validated_data)

        if users:
            for user in users:
                instance.user_set.add(user)
            instance.save()
        return instance

将添加ID为1和2的用户。

如何使用Django-Rest-Framework将现有对象分配为多对一关系？

1 个答案: