Mongoengine + Flask Tutorial

Graphene comes with builtin support to Mongoengine, which makes quite easy to operate with your current models.

Note: The code in this tutorial is pulled from the Flask Mongoengine example app.

Setup the Project

# Create the project directory
mkdir flask_graphene_mongo
cd flask_graphene_mongo

# [Optional but suggested] Create a virtualenv to isolate our package dependencies locally
virtualenv env
source env/bin/activate

# Install required packages
pip install Flask
pip install Flask-GraphQL
pip install graphene-mongo

# Install mongomock or you have to run a real mongo server instance somewhere.
pip install mongomock

Defining our models

Let’s get start with following models:

# flask_graphene_mongo/models.py
from datetime import datetime
from mongoengine import Document
from mongoengine.fields import (
    DateTimeField, ReferenceField, StringField,
)


class Department(Document):
    meta = {'collection': 'department'}
    name = StringField()


class Role(Document):
    meta = {'collection': 'role'}
    name = StringField()


class Employee(Document):
    meta = {'collection': 'employee'}
    name = StringField()
    hired_on = DateTimeField(default=datetime.now)
    department = ReferenceField(Department)
    role = ReferenceField(Role)

Schema

Here I assume you guys have the basic knowledage of how schema works in GraphQL, that I define the root type as the Query class below with the ability to list all employees.

# flask_graphene_mongo/schema.py
import graphene
from graphene.relay import Node
from graphene_mongo import MongoengineConnectionField, MongoengineObjectType
from models import Department as DepartmentModel
from models import Employee as EmployeeModel
from models import Role as RoleModel

class Department(MongoengineObjectType):

    class Meta:
        model = DepartmentModel
        interfaces = (Node,)


class Role(MongoengineObjectType):

    class Meta:
        model = RoleModel
        interfaces = (Node,)


class Employee(MongoengineObjectType):

    class Meta:
        model = EmployeeModel
        interfaces = (Node,)


class Query(graphene.ObjectType):
    node = Node.Field()
    all_employees = MongoengineConnectionField(Employee)
    all_role = MongoengineConnectionField(Role)
    role = graphene.Field(Role)

schema = graphene.Schema(query=Query, types=[Department, Employee, Role])

Creating some data

By putting some data to make this demo can run directly:

# flask_graphene_mongo/database.py
from mongoengine import connect

from models import Department, Employee, Role

# You can connect to a real mongo server instance by your own.
connect('graphene-mongo-example', host='mongomock://localhost', alias='default')


def init_db():
    # Create the fixtures
    engineering = Department(name='Engineering')
    engineering.save()

    hr = Department(name='Human Resources')
    hr.save()

    manager = Role(name='manager')
    manager.save()

    engineer = Role(name='engineer')
    engineer.save()

    peter = Employee(name='Peter', department=engineering, role=engineer)
    peter.save()

    roy = Employee(name='Roy', department=engineering, role=engineer)
    roy.save()

    tracy = Employee(name='Tracy', department=hr, role=manager)
    tracy.save()

Creating GraphQL and GraphiQL views in Flask

There is only one URL from which GraphQL is accessed, and we take the advantage of Flask-GraphQL to generate the GraphQL interface for easily accessed by a browser:

# flask_graphene_mongo/app.py
from database import init_db
from flask import Flask
from flask_graphql import GraphQLView
from schema import schema

app = Flask(__name__)
app.debug = True

default_query = '''
{
  allEmployees {
    edges {
      node {
        id,
        name,
        department {
          id,
          name
        },
        role {
          id,
          name
        }
      }
    }
  }
}'''.strip()

app.add_url_rule(
    '/graphql',
    view_func=GraphQLView.as_view('graphql', schema=schema, graphiql=True)
)

if __name__ == '__main__':
    init_db()
    app.run()

Testing

We are ready to launch the server!

$ python app.py
    * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Then go to http://localhost:5000/graphql to test your first query.