CODEWITHSUNDEEP
djangojsongispostgisgeodjango
Bibhas Debnath
Bibhas Debnath

Reputation: 14929

Get Django GeometryField's coordinates with values()

I have a model with a GeometryField. Like this - 

from django.contrib.gis.db import models as geo_models

class School(BaseModel):
    # Some fields
    centroid = geo_models.GeometryField(blank=True, null=True)

And I'm filtering the values with the values() method because I have to generate a JSON out of the QuerySet - 

class SearchView(View, JSONResponseMixin):
    def get(self, *args, **kwargs):
        params = self.request.GET
        results = {}
        schools = School.objects.values('id', 'code', 'name')
        # More stuff here

But I need to return the latitude and longitude in the JSON too. Putting centroid in values() just returns the encrypted hex value. How do I get it to spit the coordinates out?

Upvotes: 3

Views: 1315

Answers (1)

Bibhas Debnath
Bibhas Debnath

Reputation: 14929

After much research, had to use the ST_AsGeoJSON() function of PostGIS like this - 

schools = School.objects.extra(
    select={
        'centroid': 'ST_AsGeoJSON("schools_school"."centroid")'
    }
).values('code', 'name', 'centroid')

As a result, I get the JSON compatible data - 

{
    "results": [
        {
            "code": "12345678",
            "centroid": "{\"type\":\"Point\",\"coordinates\":[75.32559653,16.906422997]}",
            "name": "SCHOOL NAME"
        },
        // more
    ]
}

I'd still have to deserialize it on client side, but I guess that's doable and acceptable. At least I get JSON.

Upvotes: 3

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