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539 lines
13 KiB
ReStructuredText
539 lines
13 KiB
ReStructuredText
Introduction tutorial - Graphene and Django
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===========================================
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Graphene has a number of additional features that are designed to make
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working with Django *really simple*.
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Our primary focus here is to give a good understanding of how to connect models from Django ORM to graphene object types.
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A good idea is to check the `graphene <http://docs.graphene-python.org/en/latest/>`__ documentation first.
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Set up the Django project
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-------------------------
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You can find the entire project in ``examples/cookbook-plain``.
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----
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We will set up the project, create the following:
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- A Django project called ``cookbook``
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- An app within ``cookbook`` called ``ingredients``
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.. code:: bash
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# Create the project directory
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mkdir cookbook
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cd cookbook
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# Create a virtualenv to isolate our package dependencies locally
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virtualenv env
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source env/bin/activate # On Windows use `env\Scripts\activate`
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# Install Django and Graphene with Django support
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pip install django
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pip install graphene_django
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# Set up a new project with a single application
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django-admin.py startproject cookbook . # Note the trailing '.' character
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cd cookbook
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django-admin.py startapp ingredients
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Now sync your database for the first time:
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.. code:: bash
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python manage.py migrate
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Let's create a few simple models...
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Defining our models
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^^^^^^^^^^^^^^^^^^^
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Let's get started with these models:
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.. code:: python
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# cookbook/ingredients/models.py
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from django.db import models
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class Category(models.Model):
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name = models.CharField(max_length=100)
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def __str__(self):
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return self.name
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class Ingredient(models.Model):
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name = models.CharField(max_length=100)
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notes = models.TextField()
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category = models.ForeignKey(
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Category, related_name='ingredients', on_delete=models.CASCADE)
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def __str__(self):
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return self.name
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Add ingredients as INSTALLED_APPS:
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.. code:: python
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INSTALLED_APPS = [
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...
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# Install the ingredients app
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'cookbook.ingredients',
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]
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Don't forget to create & run migrations:
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.. code:: bash
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python manage.py makemigrations
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python manage.py migrate
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Load some test data
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^^^^^^^^^^^^^^^^^^^
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Now is a good time to load up some test data. The easiest option will be
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to `download the
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ingredients.json <https://raw.githubusercontent.com/graphql-python/graphene-django/master/examples/cookbook/cookbook/ingredients/fixtures/ingredients.json>`__
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fixture and place it in
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``cookbook/ingredients/fixtures/ingredients.json``. You can then run the
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following:
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.. code:: bash
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$ python ./manage.py loaddata ingredients
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Installed 6 object(s) from 1 fixture(s)
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Alternatively you can use the Django admin interface to create some data
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yourself. You'll need to run the development server (see below), and
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create a login for yourself too (``./manage.py createsuperuser``).
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Register models with admin panel:
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.. code:: python
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# cookbook/ingredients/admin.py
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from django.contrib import admin
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from cookbook.ingredients.models import Category, Ingredient
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admin.site.register(Category)
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admin.site.register(Ingredient)
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Hello GraphQL - Schema and Object Types
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---------------------------------------
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In order to make queries to our Django project, we are going to need few things:
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* Schema with defined object types
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* A view, taking queries as input and returning the result
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GraphQL presents your objects to the world as a graph structure rather
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than a more hierarchical structure to which you may be accustomed. In
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order to create this representation, Graphene needs to know about each
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*type* of object which will appear in the graph.
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This graph also has a *root type* through which all access begins. This
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is the ``Query`` class below.
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This means, for each of our models, we are going to create a type, subclassing ``DjangoObjectType``
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After we've done that, we will list those types as fields in the ``Query`` class.
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Create ``cookbook/ingredients/schema.py`` and type the following:
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.. code:: python
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# cookbook/ingredients/schema.py
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import graphene
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from graphene_django.types import DjangoObjectType
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from cookbook.ingredients.models import Category, Ingredient
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class CategoryType(DjangoObjectType):
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class Meta:
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model = Category
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class IngredientType(DjangoObjectType):
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class Meta:
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model = Ingredient
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class Query(object):
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all_categories = graphene.List(CategoryType)
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all_ingredients = graphene.List(IngredientType)
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def resolve_all_categories(self, info, **kwargs):
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return Category.objects.all()
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def resolve_all_ingredients(self, info, **kwargs):
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# We can easily optimize query count in the resolve method
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return Ingredient.objects.select_related('category').all()
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Note that the above ``Query`` class is a mixin, inheriting from
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``object``. This is because we will now create a project-level query
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class which will combine all our app-level mixins.
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Create the parent project-level ``cookbook/schema.py``:
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.. code:: python
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import graphene
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import cookbook.ingredients.schema
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class Query(cookbook.ingredients.schema.Query, graphene.ObjectType):
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# This class will inherit from multiple Queries
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# as we begin to add more apps to our project
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pass
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schema = graphene.Schema(query=Query)
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You can think of this as being something like your top-level ``urls.py``
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file (although it currently lacks any namespacing).
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Testing everything so far
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-------------------------
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We are going to do some configuration work, in order to have a working Django where we can test queries, before we move on, updating our schema.
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Update settings
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^^^^^^^^^^^^^^^
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Next, install your app and GraphiQL in your Django project. GraphiQL is
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a web-based integrated development environment to assist in the writing
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and executing of GraphQL queries. It will provide us with a simple and
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easy way of testing our cookbook project.
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Add ``graphene_django`` to ``INSTALLED_APPS`` in ``cookbook/settings.py``:
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.. code:: python
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INSTALLED_APPS = [
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...
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# This will also make the `graphql_schema` management command available
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'graphene_django',
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]
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And then add the ``SCHEMA`` to the ``GRAPHENE`` config in ``cookbook/settings.py``:
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.. code:: python
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GRAPHENE = {
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'SCHEMA': 'cookbook.schema.schema'
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}
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Alternatively, we can specify the schema to be used in the urls definition,
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as explained below.
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Creating GraphQL and GraphiQL views
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Unlike a RESTful API, there is only a single URL from which GraphQL is
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accessed. Requests to this URL are handled by Graphene's ``GraphQLView``
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view.
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This view will serve as GraphQL endpoint. As we want to have the
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aforementioned GraphiQL we specify that on the parameters with ``graphiql=True``.
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.. code:: python
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from django.conf.urls import url, include
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from django.contrib import admin
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from graphene_django.views import GraphQLView
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urlpatterns = [
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url(r'^admin/', admin.site.urls),
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url(r'^graphql', GraphQLView.as_view(graphiql=True)),
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]
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If we didn't specify the target schema in the Django settings file
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as explained above, we can do so here using:
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.. code:: python
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from django.conf.urls import url, include
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from django.contrib import admin
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from graphene_django.views import GraphQLView
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from cookbook.schema import schema
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urlpatterns = [
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url(r'^admin/', admin.site.urls),
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url(r'^graphql', GraphQLView.as_view(graphiql=True, schema=schema)),
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]
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Testing our GraphQL schema
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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We're now ready to test the API we've built. Let's fire up the server
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from the command line.
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.. code:: bash
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$ python ./manage.py runserver
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Performing system checks...
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Django version 1.9, using settings 'cookbook.settings'
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Starting development server at http://127.0.0.1:8000/
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Quit the server with CONTROL-C.
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Go to `localhost:8000/graphql <http://localhost:8000/graphql>`__ and
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type your first query!
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.. code::
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query {
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allIngredients {
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id
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name
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}
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}
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If you are using the provided fixtures, you will see the following response:
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.. code::
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{
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"data": {
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"allIngredients": [
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{
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"id": "1",
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"name": "Eggs"
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},
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{
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"id": "2",
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"name": "Milk"
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},
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{
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"id": "3",
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"name": "Beef"
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},
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{
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"id": "4",
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"name": "Chicken"
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}
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]
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}
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}
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You can experiment with ``allCategories`` too.
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Something to have in mind is the `auto camelcasing <http://docs.graphene-python.org/en/latest/types/schema/#auto-camelcase-field-names>`__ that is happening.
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Getting relations
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-----------------
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Right now, with this simple setup in place, we can query for relations too. This is where graphql becomes really powerful!
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For example, we may want to list all categories and in each category, all ingredients that are in that category.
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We can do that with the following query:
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.. code::
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query {
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allCategories {
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id
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name
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ingredients {
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id
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name
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}
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}
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}
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This will give you (in case you are using the fixtures) the following result:
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.. code::
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{
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"data": {
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"allCategories": [
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{
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"id": "1",
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"name": "Dairy",
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"ingredients": [
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{
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"id": "1",
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"name": "Eggs"
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},
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{
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"id": "2",
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"name": "Milk"
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}
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]
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},
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{
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"id": "2",
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"name": "Meat",
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"ingredients": [
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{
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"id": "3",
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"name": "Beef"
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},
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{
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"id": "4",
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"name": "Chicken"
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}
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]
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}
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]
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}
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}
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We can also list all ingredients and get information for the category they are in:
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.. code::
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query {
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allIngredients {
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id
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name
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category {
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id
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name
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}
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}
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}
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Getting single objects
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----------------------
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So far, we have been able to fetch list of objects and follow relation. But what about single objects?
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We can update our schema to support that, by adding new query for ``ingredient`` and ``category`` and adding arguments, so we can query for specific objects.
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.. code:: python
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import graphene
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from graphene_django.types import DjangoObjectType
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from cookbook.ingredients.models import Category, Ingredient
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class CategoryType(DjangoObjectType):
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class Meta:
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model = Category
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class IngredientType(DjangoObjectType):
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class Meta:
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model = Ingredient
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class Query(object):
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category = graphene.Field(CategoryType,
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id=graphene.Int(),
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name=graphene.String())
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all_categories = graphene.List(CategoryType)
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ingredient = graphene.Field(IngredientType,
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id=graphene.Int(),
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name=graphene.String())
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all_ingredients = graphene.List(IngredientType)
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def resolve_all_categories(self, info, **kwargs):
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return Category.objects.all()
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def resolve_all_ingredients(self, info, **kwargs):
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return Ingredient.objects.all()
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def resolve_category(self, info, **kwargs):
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id = kwargs.get('id')
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name = kwargs.get('name')
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if id is not None:
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return Category.objects.get(pk=id)
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if name is not None:
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return Category.objects.get(name=name)
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return None
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def resolve_ingredient(self, info, **kwargs):
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id = kwargs.get('id')
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name = kwargs.get('name')
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if id is not None:
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return Ingredient.objects.get(pk=id)
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if name is not None:
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return Ingredient.objects.get(name=name)
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return None
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Now, with the code in place, we can query for single objects.
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For example, lets query ``category``:
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.. code::
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query {
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category(id: 1) {
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name
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}
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anotherCategory: category(name: "Dairy") {
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ingredients {
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id
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name
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}
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}
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}
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This will give us the following results:
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.. code::
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{
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"data": {
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"category": {
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"name": "Dairy"
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},
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"anotherCategory": {
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"ingredients": [
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{
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"id": "1",
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"name": "Eggs"
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},
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{
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"id": "2",
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"name": "Milk"
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}
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]
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}
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}
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}
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As an exercise, you can try making some queries to ``ingredient``.
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Something to keep in mind - since we are using one field several times in our query, we need `aliases <http://graphql.org/learn/queries/#aliases>`__
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Summary
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-------
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As you can see, GraphQL is very powerful but there are a lot of repetitions in our example. We can do a lot of improvements by adding layers of abstraction on top of ``graphene-django``.
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If you want to put things like ``django-filter`` and automatic pagination in action, you should continue with the **relay tutorial.**
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