Defining Fields¶

Fields can be defined manually or auto type can be used for automatic type resolution. All basic field types and relation fields are supported out of the box. If you use a library that defines a custom field you will need to define an equivalent type such as str, float, bool, int or id.

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import strawberry_django
from strawberry import auto

@strawberry_django.type(models.Fruit)
class Fruit:
    id: auto
    name: auto

# equivalent type, inferred by `strawberry`

@strawberry_django.type(models.Fruit)
class Fruit2:
    id: strawberry.ID
    name: str

Relationships¶

All one-to-one, one-to-many, many-to-one and many-to-many relationship types are supported, and the many-to-many relation is described using the typing.List annotation. The default resolver of strawberry_django.fields() resolves the relationship based on given type information.

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from typing import List

@strawberry_django.type(models.Fruit)
class Fruit:
    id: auto
    name: auto
    color: "Color"


@strawberry_django.type(models.Color)
class Color:
    id: auto
    name: auto
    fruits: List[Fruit]

Note that all relations can naturally trigger the n+1 problem. To avoid that, you can either enable the Optimizer Extension which will automatically solve some general issues for you, or even use Data Loaders for more complex situations.

Field customization¶

All Django types are encoded using the strawberry_django.field() field type by default. Fields can be customized with various parameters.

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@strawberry_django.type(models.Color)
class Color:
    another_name: auto = strawberry_django.field(field_name='name')
    internal_name: auto = strawberry_django.field(
        name='fruits',
        field_name='fruit_set',
        filters=FruitFilter,
        order=FruitOrder,
        pagination=True,
        description="A list of fruits with this color"
    )

Defining types for auto fields¶

When using strawberry.auto to resolve a field's type, Strawberry Django uses a dict that maps each django field field type to its proper type. e.g.:

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{
    models.CharField: str,
    models.IntegerField: int,
    ...,
}

If you are using a custom django field that is not part of the default library, or you want to use a different type for a field, you can do that by overriding its value in the map, like:

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from typing import NewType

from django.db import models
import strawberry
import strawberry_django
from strawberry_django.fields.types import field_type_map

Slug = strawberry.scalar(
    NewType("Slug", str),
    serialize=lambda v: v,
    parse_value=lambda v: v,
)

@strawberry_django.type
class MyCustomFileType:
    ...

field_type_map.update({
    models.SlugField: Slug,
    models.FileField: MyCustomFileType,
})

Including / excluding Django model fields by name¶

strawberry_django.type includes two optional keyword fields to help you populate fields from the Django model, fields and exclude.

Valid values for fields are:

• __all__ to assign strawberry.auto as the field type for all model fields.
• [<List of field names>] to assign strawberry.auto as the field type for the enumerated fields. These can be combined with manual type annotations if needed.

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@strawberry_django.type(models.Fruit, fields="__all__")
class FruitType:
    pass

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@strawberry_django.type(models.Fruit, fields=["name", "color"])
class FruitType:
    pass

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@strawberry_django.type(models.Fruit, fields=["color"])
class FruitType:
    name: str

Valid values for exclude are:

• [<List of field names>] to exclude from the fields list. All other Django model fields will included and have strawberry.auto as the field type. These can also be overriden if another field type should be assigned. An empty list is ignored.

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@strawberry_django.type(models.Fruit, exclude=["name"])
class FruitType:
    pass

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@strawberry_django.type(models.Fruit, exclude=["name"])
class FruitType:
    color: int

Note that fields has precedence over exclude, so if both are provided, then exclude is ignored.

Overriding the field class (advanced)¶

If in your project, you want to change/add some of the standard strawberry_django.field() behaviour, it is possible to use your own custom field class when decorating a strawberry_django.type with the field_cls argument, e.g.

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class CustomStrawberryDjangoField(StrawberryDjangoField):
    """Your custom behaviour goes here."""

@strawberry_django.type(User, field_cls=CustomStrawberryDjangoField)
class UserType:
    # Each of these fields will be an instance of `CustomStrawberryDjangoField`.
    id: int
    name: auto


@strawberry.type
class UserQuery:
    # You can directly create your custom field class on a plain strawberry type
    user: UserType = CustomStrawberryDjangoField()

In this example, each of the fields of the UserType will be automatically created by CustomStrawberryDjangoField, which may implement anything from custom pagination of relationships to altering the field permissions.