Introduction tutorial - Graphene and Django

Graphene has a number of additional features that are designed to make working with Django really simple.

Our primary focus here is to give a good understanding of how to connect models from Django ORM to graphene object types.

A good idea is to check the graphene documentation first.

Set up the Django project

You can find the entire project in examples/cookbook-plain.


We will set up the project, create the following:

  • A Django project called cookbook
  • An app within cookbook called ingredients
# Create the project directory
mkdir cookbook
cd cookbook

# Create a virtualenv to isolate our package dependencies locally
virtualenv env
source env/bin/activate  # On Windows use `env\Scripts\activate`

# Install Django and Graphene with Django support
pip install django
pip install graphene_django

# Set up a new project with a single application
django-admin.py startproject cookbook .  # Note the trailing '.' character
cd cookbook
django-admin.py startapp ingredients

Now sync your database for the first time:

python manage.py migrate

Let’s create a few simple models…

Defining our models

Let’s get started with these models:

# cookbook/ingredients/models.py
from django.db import models


class Category(models.Model):
    name = models.CharField(max_length=100)

    def __str__(self):
        return self.name


class Ingredient(models.Model):
    name = models.CharField(max_length=100)
    notes = models.TextField()
    category = models.ForeignKey(Category, related_name='ingredients',
       on_delete=models.CASCADE)

    def __str__(self):
        return self.name

Add ingredients as INSTALLED_APPS:

INSTALLED_APPS = [
    ...
    # Install the ingredients app
    'cookbook.ingredients',
]

Don’t forget to create & run migrations:

python manage.py makemigrations
python manage.py migrate

Load some test data

Now is a good time to load up some test data. The easiest option will be to download the ingredients.json fixture and place it in cookbook/ingredients/fixtures/ingredients.json. You can then run the following:

$ python ./manage.py loaddata ingredients

Installed 6 object(s) from 1 fixture(s)

Alternatively you can use the Django admin interface to create some data yourself. You’ll need to run the development server (see below), and create a login for yourself too (./manage.py createsuperuser).

Hello GraphQL - Schema and Object Types

In order to make queries to our Django project, we are going to need few things:

  • Schema with defined object types
  • A view, taking queries as input and returning the result

GraphQL presents your objects to the world as a graph structure rather than a more hierarchical structure to which you may be accustomed. In order to create this representation, Graphene needs to know about each type of object which will appear in the graph.

This graph also has a root type through which all access begins. This is the Query class below.

This means, for each of our models, we are going to create a type, subclassing DjangoObjectType

After we’ve done that, we will list those types as fields in the Query class.

Create cookbook/ingredients/schema.py and type the following:

# cookbook/ingredients/schema.py
import graphene

from graphene_django.types import DjangoObjectType

from cookbook.ingredients.models import Category, Ingredient


class CategoryType(DjangoObjectType):
    class Meta:
        model = Category


class IngredientType(DjangoObjectType):
    class Meta:
        model = Ingredient


class Query(object):
    all_categories = graphene.List(CategoryType)
    all_ingredients = graphene.List(IngredientType)

    def resolve_all_categories(self, info, **kwargs):
        return Category.objects.all()

    def resolve_all_ingredients(self, info, **kwargs):
        # We can easily optimize query count in the resolve method
        return Ingredient.objects.select_related('category').all()

Note that the above Query class is marked as ‘abstract’. This is because we will now create a project-level query which will combine all our app-level queries.

Create the parent project-level cookbook/schema.py:

import graphene

import cookbook.ingredients.schema


class Query(cookbook.ingredients.schema.Query, graphene.ObjectType):
    # This class will inherit from multiple Queries
    # as we begin to add more apps to our project
    pass

schema = graphene.Schema(query=Query)

You can think of this as being something like your top-level urls.py file (although it currently lacks any namespacing).

Testing everything so far

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.

Update settings

Next, install your app and GraphiQL in your Django project. GraphiQL is a web-based integrated development environment to assist in the writing and executing of GraphQL queries. It will provide us with a simple and easy way of testing our cookbook project.

Add graphene_django to INSTALLED_APPS in cookbook/settings.py:

INSTALLED_APPS = [
    ...
    # This will also make the `graphql_schema` management command available
    'graphene_django',
]

And then add the SCHEMA to the GRAPHENE config in cookbook/settings.py:

GRAPHENE = {
    'SCHEMA': 'cookbook.schema.schema'
}

Alternatively, we can specify the schema to be used in the urls definition, as explained below.

Creating GraphQL and GraphiQL views

Unlike a RESTful API, there is only a single URL from which GraphQL is accessed. Requests to this URL are handled by Graphene’s GraphQLView view.

This view will serve as GraphQL endpoint. As we want to have the aforementioned GraphiQL we specify that on the parameters with graphiql=True.

from django.conf.urls import url, include
from django.contrib import admin

from graphene_django.views import GraphQLView

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^graphql', GraphQLView.as_view(graphiql=True)),
]

If we didn’t specify the target schema in the Django settings file as explained above, we can do so here using:

from django.conf.urls import url, include
from django.contrib import admin

from graphene_django.views import GraphQLView

from cookbook.schema import schema

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^graphql', GraphQLView.as_view(graphiql=True, schema=schema)),
]

Testing our GraphQL schema

We’re now ready to test the API we’ve built. Let’s fire up the server from the command line.

$ python ./manage.py runserver

Performing system checks...
Django version 1.9, using settings 'cookbook.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Go to localhost:8000/graphql and type your first query!

query {
  allIngredients {
    id
    name
  }
}

If you are using the provided fixtures, you will see the following response:

{
  "data": {
    "allIngredients": [
      {
        "id": "1",
        "name": "Eggs"
      },
      {
        "id": "2",
        "name": "Milk"
      },
      {
        "id": "3",
        "name": "Beef"
      },
      {
        "id": "4",
        "name": "Chicken"
      }
    ]
  }
}

You can experiment with allCategories too.

Something to have in mind is the auto camelcasing that is happening.

Getting relations

Right now, with this simple setup in place, we can query for relations too. This is where graphql becomes really powerful!

For example, we may want to list all categories and in each category, all ingredients that are in that category.

We can do that with the following query:

query {
  allCategories {
    id
    name
    ingredients {
      id
      name
    }
  }
}

This will give you (in case you are using the fixtures) the following result:

{
  "data": {
    "allCategories": [
      {
        "id": "1",
        "name": "Dairy",
        "ingredients": [
          {
            "id": "1",
            "name": "Eggs"
          },
          {
            "id": "2",
            "name": "Milk"
          }
        ]
      },
      {
        "id": "2",
        "name": "Meat",
        "ingredients": [
          {
            "id": "3",
            "name": "Beef"
          },
          {
            "id": "4",
            "name": "Chicken"
          }
        ]
      }
    ]
  }
}

We can also list all ingredients and get information for the category they are in:

query {
  allIngredients {
    id
    name
    category {
      id
      name
    }
  }
}

Getting single objects

So far, we have been able to fetch list of objects and follow relation. But what about single objects?

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.

import graphene

from graphene_django.types import DjangoObjectType

from cookbook.ingredients.models import Category, Ingredient


class CategoryType(DjangoObjectType):
    class Meta:
        model = Category


class IngredientType(DjangoObjectType):
    class Meta:
        model = Ingredient


class Query(object):
    category = graphene.Field(CategoryType,
                              id=graphene.Int(),
                              name=graphene.String())
    all_categories = graphene.List(CategoryType)


    ingredient = graphene.Field(IngredientType,
                                id=graphene.Int(),
                                name=graphene.String())
    all_ingredients = graphene.List(IngredientType)

    def resolve_all_categories(self, info, **kwargs):
        return Category.objects.all()

    def resolve_all_ingredients(self, info, **kwargs):
        return Ingredient.objects.all()

    def resolve_category(self, info, **kwargs):
        id = kwargs.get('id')
        name = kwargs.get('name')

        if id is not None:
            return Category.objects.get(pk=id)

        if name is not None:
            return Category.objects.get(name=name)

        return None

    def resolve_ingredient(self, info, **kwargs):
        id = kwargs.get('id')
        name = kwargs.get('name')

        if id is not None:
            return Ingredient.objects.get(pk=id)

        if name is not None:
            return Ingredient.objects.get(name=name)

        return None

Now, with the code in place, we can query for single objects.

For example, lets query category:

query {
  category(id: 1) {
    name
  }
  anotherCategory: category(name: "Dairy") {
    ingredients {
      id
      name
    }
  }
}

This will give us the following results:

{
  "data": {
    "category": {
      "name": "Dairy"
    },
    "anotherCategory": {
      "ingredients": [
        {
          "id": "1",
          "name": "Eggs"
        },
        {
          "id": "2",
          "name": "Milk"
        }
      ]
    }
  }
}

As an exercise, you can try making some queries to ingredient.

Something to keep in mind - since we are using one field several times in our query, we need aliases

Summary

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.

If you want to put things like django-filter and automatic pagination in action, you should continue with the relay tutorial.