Mutations

Warning

All the extra features provided by this lib were contributed and merged directly into the official strawberry-graphql-django lib. Since then this lib is deprecated and the official integration should be used instead.

If you were using this lib before, check out the migration guide for more information on how to migrate your code.

This library provides 3 CUD mutations for streamlining common create/update/delete operations and reducing boilerplate code. There is also a facility for creating custom mutations with automatic ValidationError support.

CUD mutations¶

gql.django.create_mutation: Will create the model using the data from the given input, returning a types.OperationInfo if it fails with all raised ValidationError data.
gql.django.update_mutation: Will update the model using the data from the given input, returning a types.OperationInfo if it fails with all raised ValidationError data.
gql.django.delete_mutation: Will delete the model using the id from the given input, returning a types.OperationInfo if it fails with all raised ValidationError data.

A simple complete example would be:

from strawberry_django_plus import gql

@gql.django.type(SomeModel)
class SomeModelType(gql.Node):
    name: gql.auto

@gql.django.input(SomeModel)
class SomeModelInput:
    name: gql.auto


@gql.django.partial(SomeModel)
class SomeModelInputPartial(gql.NodeInput):
    name: gql.auto

@gql.type
class Mutation:
    create_model: SomeModelType = gql.django.create_mutation(SomeModelInput)
    update_model: SomeModelType = gql.django.update_mutation(SomeModelInputPartial)
    delete_model: SomeModelType = gql.django.delete_mutation(gql.NodeInput)

Extending build in CUD mutations¶

There might be the need to perform some pre or post validation before running the built-in mutations. A common use case is for example setting a model field based on the current request context.

As the syntax is not completely straightforward at the moment an example is listed as follows.

from django.conf import settings
from django.db import models

# Django Model
class Asset(models.Model):
    name = models.TextField(null=True, blank=True)
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=True, blank=True)

The strawberry code uses a relay implementation but the concept should also work in a non-relay context.

from strawberry_django_plus.mutations import resolvers

@gql.django.type(Asset)
class AssetNode(gql.relay.Node):
    name: gql.auto
    owner: UserNode

@gql.django.partial(Asset)
class UpdateAssetInput(gql.NodeInput):
    name: gql.auto

@gql.type
class ModelMutation:

    @gql.mutation
    def update_asset(self, info: Info, input: UpdateAssetInput) -> ModelNode:
        data = vars(input)
        node_id: gql.relay.GlobalID = data.pop('id')
        asset: Asset = node_id.resolve_node(info, ensure_type=Asset)

        if asset.owner != info.context.request.user:
            raise PermissionError("You can only modify objects you own.")

        return resolvers.update(info, asset, resolvers.parse_input(info, data))

Important to note is that the input has to be converted via vars call. The concept is taken from the built-in mutation. You then need to call the resolvers.update function to mutate the model instance. The main benefit is that you keep all the validation and update logic from the built-in mutation.

Custom model mutations¶

It is possible to create custom model mutations with gql.django.input_mutation, which will automatically convert the arguments to an input type and mark the return value as a union between the type annotation and types.OperationInfo. The latter will be returned if the resolver raises ValidationError.

For example:

from django.core.exceptions import ValidationError
from strawberry_django_plus import gql

@gql.type
class Mutation:
    @gql.django.input_mutation
    def set_model_name(self, info, id: GlobalID, name: str) -> ModelType:
        obj = id.resolve_node(info)
        if obj.some_field == "some_value":
            raise ValidationError("Cannot update obj with some_value")

        obj.name = name
        obj.save()
        return obj