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GeoJSON support for Django GraphQL

Project description

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GeoJSON support for Django GraphQL

Dependencies

  • Python ≥ 3.4

  • Django ≥ 1.11

Installation

Install last stable version from Pypi.

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

from django.contrib.gis.db import models


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

schema.py

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

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

Geometry Type

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

schema.py

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

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):

"POINT(5 23)"
  • Hexadecimal (HEX):

"010100000000000000000014400000000000003740"
  • GeoJSON:

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

GeometryFilterSet

Django GraphQL GeoJSON provides a custom FilterSet for spatial lookups.

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

filters.py

from graphql_geojson.filters import GeometryFilterSet


class PlaceFilter(GeometryFilterSet):

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

schema.py

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

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

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

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