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