graphene-django/docs/mutations.rst

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Mutations
=========
Introduction
------------
Graphene-Django makes it easy to perform mutations.
With Graphene-Django we can take advantage of pre-existing Django features to
quickly build CRUD functionality, while still using the core `graphene mutation <https://docs.graphene-python.org/en/latest/types/mutations/>`__
features to add custom mutations to a Django project.
Simple example
--------------
.. code:: python
import graphene
from graphene_django import DjangoObjectType
from .models import Question
class QuestionType(DjangoObjectType):
class Meta:
model = Question
class QuestionMutation(graphene.Mutation):
class Arguments:
# The input arguments for this mutation
text = graphene.String(required=True)
id = graphene.ID()
# The class attributes define the response of the mutation
question = graphene.Field(QuestionType)
def mutate(self, info, text, id):
question = Question.objects.get(pk=id)
question.text = text
question.save()
# Notice we return an instance of this mutation
return QuestionMutation(question=question)
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class Mutation(graphene.ObjectType):
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update_question = QuestionMutation.Field()
Django Forms
------------
Graphene-Django comes with mutation classes that will convert the fields on Django forms into inputs on a mutation.
DjangoFormMutation
~~~~~~~~~~~~~~~~~~
.. code:: python
from graphene_django.forms.mutation import DjangoFormMutation
class MyForm(forms.Form):
name = forms.CharField()
class MyMutation(DjangoFormMutation):
class Meta:
form_class = MyForm
``MyMutation`` will automatically receive an ``input`` argument. This argument should be a ``dict`` where the key is ``name`` and the value is a string.
DjangoModelFormMutation
~~~~~~~~~~~~~~~~~~~~~~~
``DjangoModelFormMutation`` will pull the fields from a ``ModelForm``.
.. code:: python
from graphene_django.forms.mutation import DjangoModelFormMutation
class Pet(models.Model):
name = models.CharField()
class PetForm(forms.ModelForm):
class Meta:
model = Pet
fields = ('name',)
# This will get returned when the mutation completes successfully
class PetType(DjangoObjectType):
class Meta:
model = Pet
class PetMutation(DjangoModelFormMutation):
pet = Field(PetType)
class Meta:
form_class = PetForm
``PetMutation`` will grab the fields from ``PetForm`` and turn them into inputs. If the form is valid then the mutation
will lookup the ``DjangoObjectType`` for the ``Pet`` model and return that under the key ``pet``. Otherwise it will
return a list of errors.
You can change the input name (default is ``input``) and the return field name (default is the model name lowercase).
.. code:: python
class PetMutation(DjangoModelFormMutation):
class Meta:
form_class = PetForm
input_field_name = 'data'
return_field_name = 'my_pet'
Form validation
~~~~~~~~~~~~~~~
Form mutations will call ``is_valid()`` on your forms.
If the form is valid then the class method ``perform_mutate(form, info)`` is called on the mutation. Override this method
to change how the form is saved or to return a different Graphene object type.
If the form is *not* valid then a list of errors will be returned. These errors have two fields: ``field``, a string
containing the name of the invalid form field, and ``messages``, a list of strings with the validation messages.
Django REST Framework
---------------------
You can re-use your Django Rest Framework serializer with Graphene Django mutations.
You can create a Mutation based on a serializer by using the `SerializerMutation` base class:
.. code:: python
from graphene_django.rest_framework.mutation import SerializerMutation
class MyAwesomeMutation(SerializerMutation):
class Meta:
serializer_class = MySerializer
Create/Update Operations
~~~~~~~~~~~~~~~~~~~~~~~~
By default ModelSerializers accept create and update operations. To
customize this use the `model_operations` attribute on the ``SerializerMutation`` class.
The update operation looks up models by the primary key by default. You can
customize the look up with the ``lookup_field`` attribute on the ``SerializerMutation`` class.
.. code:: python
from graphene_django.rest_framework.mutation import SerializerMutation
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from .serializers import MyModelSerializer
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class AwesomeModelMutation(SerializerMutation):
class Meta:
serializer_class = MyModelSerializer
model_operations = ['create', 'update']
lookup_field = 'id'
Overriding Update Queries
~~~~~~~~~~~~~~~~~~~~~~~~~
Use the method ``get_serializer_kwargs`` to override how updates are applied.
.. code:: python
from graphene_django.rest_framework.mutation import SerializerMutation
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from .serializers import MyModelSerializer
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class AwesomeModelMutation(SerializerMutation):
class Meta:
serializer_class = MyModelSerializer
@classmethod
def get_serializer_kwargs(cls, root, info, **input):
if 'id' in input:
instance = Post.objects.filter(
id=input['id'], owner=info.context.user
).first()
if instance:
return {'instance': instance, 'data': input, 'partial': True}
else:
raise http.Http404
return {'data': input, 'partial': True}
Relay
-----
You can use relay with mutations. A Relay mutation must inherit from
``ClientIDMutation`` and implement the ``mutate_and_get_payload`` method:
.. code:: python
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import graphene
from graphene import relay
from graphene_django import DjangoObjectType
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from graphql_relay import from_global_id
from .queries import QuestionType
class QuestionMutation(relay.ClientIDMutation):
class Input:
text = graphene.String(required=True)
id = graphene.ID()
question = graphene.Field(QuestionType)
@classmethod
def mutate_and_get_payload(cls, root, info, text, id):
question = Question.objects.get(pk=from_global_id(id)[1])
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question.text = text
question.save()
return QuestionMutation(question=question)
Notice that the ``class Arguments`` is renamed to ``class Input`` with relay.
This is due to a deprecation of ``class Arguments`` in graphene 2.0.
Relay ClientIDMutation accept a ``clientIDMutation`` argument.
This argument is also sent back to the client with the mutation result
(you do not have to do anything). For services that manage
a pool of many GraphQL requests in bulk, the ``clientIDMutation``
allows you to match up a specific mutation with the response.