django-graphql-geojson

Django GraphQL GeoJSON

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GeoJSON_ support for Django GraphQL_

.. _GeoJSON: http://geojson.org .. _Django GraphQL: https://github.com/graphql-python/graphene-django

Dependencies

• Python ≥ 3.4
• Django ≥ 1.11

Installation

Install last stable version from Pypi.

.. code:: sh

pip install django-graphql-geojson

GeoJSONType

GeoJSONType is a subclass of DjangoObjectType which provides GraphQL fields in GeoJSON format.

Just define a Meta.geojson_field to be represented as a Geometry type.

models.py

.. code:: python

from django.contrib.gis.db import models


class Place(models.Model):
    name = models.CharField(max_length=255)
    location = models.PointField()

schema.py

.. code:: python

import graphene
import graphql_geojson


class PlaceType(graphql_geojson.GeoJSONType):

    class Meta:
        model = models.Place
        geojson_field = 'location'


class Query(graphene.ObjectType):
    places = graphene.List(PlaceType)


schema = graphene.Schema(query=Query)

Query

.. code::

query {
  places {
    id
    type
    geometry {
      type
      coordinates
    }
    bbox
    properties {
      name
    }
  }
}

Geometry Type

Geometry is a special GraphQL type that represents a GEOS geometry object_.

.. _GEOS geometry object: https://docs.djangoproject.com/en/2.0/ref/contrib/gis/geos/#geometry-objects

schema.py

.. code:: python

import graphene
import graphql_geojson


class CreatePlace(graphene.Mutation):
    place = graphene.Field(types.PlaceType)

    class Arguments:
        name = graphene.String(required=True)
        location = graphql_geojson.Geometry(required=True)

    @classmethod
    def mutate(cls, root, info, **args):
        place = models.Place.objects.create(**args)
        return cls(place=place)

Mutation

.. code::

mutation CreatePlace($name: String!, $location: Geometry!) {
  createPlace(name: $name, location: $location) {
    place {
      id
    }
  }
}

Geometry type may be initialized in a few ways:

• Well-known text (WKT):

.. code:: python

"POINT(5 23)"

• Hexadecimal (HEX):

.. code:: python

"010100000000000000000014400000000000003740"

• GeoJSON:

.. code:: python

{
  "type": "Point",
  "coordinates": [5, 23]
}

GeometryFilterSet

Django GraphQL GeoJSON provides a custom FilterSet for spatial lookups_.

.. _spatial lookups: https://docs.djangoproject.com/en/2.0/ref/contrib/gis/geoquerysets/#spatial-lookups

The Meta.fields option is combined with model to automatically generate filters.

filters.py

.. code:: python

from graphql_geojson.filters import GeometryFilterSet


class PlaceFilter(GeometryFilterSet):

    class Meta:
        model = models.Place
        fields = {
            'name': ['exact'],
            'location': ['exact', 'intersects', 'distance_lte'],
        }

schema.py

.. code:: python

import graphene
import graphql_geojson
from graphene import relay
from graphene_django.filter import DjangoFilterConnectionField


class PlaceNode(graphql_geojson.GeoJSONType):

    class Meta:
        model = Place
        interfaces = [relay.Node]
        geojson_field = 'location'


class Query(graphene.ObjectType):
    places = DjangoFilterConnectionField(
        PlaceNode,
        filterset_class=PlaceFilter)

Query

.. code::

  query Places($geometry: Geometry!){
    places(location_Intersects: $geometry) {
      edges {
        node {
          id
        }
      }
    }
  }

Distance lookups_ take a Distance parameter comprising:

• The desired unit attribute_ name
• Distance value
• A geometry to base calculations from

.. _Distance lookups: https://docs.djangoproject.com/en/2.0/ref/contrib/gis/db-api/#distance-lookups .. _unit attribute: https://docs.djangoproject.com/en/2.0/ref/contrib/gis/measure/#supported-units

.. code::

  query Places(
      $unit: DistanceUnitEnum!,
      $value: Float!,
      $geometry: Geometry!)
    {
    places(location_DistanceLte: {
        unit: $unit,
        value: $value,
        geometry: $geometry
      }) {
      edges {
        node {
          id
        }
      }
    }
  }

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