Schemas from Django models

Schemas are very useful to define your validation rules and responses, but sometimes you need to reflect your database models into schemas and keep changes in sync.

ModelSchema

ModelSchema is a special base class that can automatically generate schemas from your models.

All you need is to set model and fields attributes on your schema Meta:

from django.contrib.auth.models import User
from ninja import ModelSchema

class UserSchema(ModelSchema):
    class Meta:
        model = User
        fields = ['id', 'username', 'first_name', 'last_name']

# Will create schema like this:
# 
# class UserSchema(Schema):
#     id: int
#     username: str
#     first_name: str
#     last_name: str

Using ALL model fields

To use all fields from a model - you can pass __all__ to fields:

class UserSchema(ModelSchema):
    class Meta:
        model = User
        fields = "__all__"

Warning

Using all is not recommended.
This can lead to accidental unwanted data exposure (like hashed password, in the above example).
General advice - use fields to explicitly define list of fields that you want to be visible in API.

Excluding model fields

To use all fields except a few, you can use exclude configuration:

class UserSchema(ModelSchema):
    class Meta:
        model = User
        exclude = ['password', 'last_login', 'user_permissions']

# Will create schema like this:
# 
# class UserSchema(Schema):
#     id: int
#     username: str
#     first_name: str
#     last_name: str
#     email: str
#     is_superuser: bool
#     ... and the rest

Overriding fields

To change default annotation for some field, or to add a new field, just use annotated attributes as usual.

class GroupSchema(ModelSchema):
    class Meta:
        model = Group
        fields = ['id', 'name']


class UserSchema(ModelSchema):
    groups: List[GroupSchema] = []

    class Meta:
        model = User
        fields = ['id', 'username', 'first_name', 'last_name']

Making fields optional

Pretty often for PATCH API operations you need to make all fields of your schema optional. To do that you can use config fields_optional

class PatchGroupSchema(ModelSchema):
    class Meta:
        model = Group
        fields = ['id', 'name', 'description'] # Note: all these fields are required on model level
        fields_optional = '__all__'

also you can define just a few optional fields instead of all:

     fields_optional = ['description']