how to override _default manager used by ModelSerializer-CodePudding

Given below snippet,

class CustomManager(models.Manager):
   def create(**kwargs):
       super().create(external_id='xyz', **kwargs)

class Person(models.Model):
   internal_id = models.AutoField(db_column='id', primary_key=True)
   f_name=models.CharField(db_column='f_name', max_length=15, blank=True, null=True)
   external_id = models.CharField(db_column='ext_id', null=True, blank=True, max_length=20)
   objects = models.Manager()
   custom = CustomManager()


class PersonSerializer(serializer.ModelSerializer):
   class Meta:
     model=Person
     fields='__all__'

Here, when .save() method gets called on the serializer, the default manager used by the the create function in serializer is objects. I would like this to be changed to custom so that when save call happens, create function inside CustomManager gets invoked.

I can achieve this by overriding the super class method create in the serializer. But is there any better workaround for this without overriding base class method?

CodePudding user response：

If you look serializer's save method it will call either create or update for your request. Actually, you have two way to achieve this. First, override serializer create method;

# serializers.py

class PersonSerializer(serializer.ModelSerializer):
   class Meta:
     model = Person
     fields = "__all__"
   
   def create(self, validated_data):
       # create an instance with your custom code and return it
       return instance

off subject: do not use "__all__", mostly it's not recommended. explicitly specify your fields.

And secondly, you can set your custom manager as default manager with default_manager_name. It might be helpful; Model.Meta.default_manager_name. The default value for default_manager_name is objects.

# managers.py

from django.db import models


class CustomManager(models.Manager):
    def create(self, **kwargs):
        # your logic here
        return obj

# models.py

class Person(models.Model):
    internal_id = models.AutoField(db_column='id', primary_key=True)
    f_name=models.CharField(db_column='f_name', max_length=15, blank=True, null=True)
    external_id = models.CharField(db_column='ext_id', null=True, blank=True, max_length=20)

    objects = models.Manager()
    custom = CustomManager()
    
    class Meta:
        default_manager_name = "custom"

But be careful because this method will be work only if you use create method like serializers do; Person._default_manager.create(**kwargs).

Lastly, you need to run Django's makemigrations and migrate commands.