Use HttpResponse with JSON data in this code

Question

This code seems to work fine when I used Django console and just print it.

reference = FloodHazard.objects.filter(hazard='High')
ids = reference.values_list('id', flat=True)

for myid in ids:
    getgeom = FloodHazard.objects.get(id=myid).geom
    response = BuildingStructure.objects.filter(geom__intersects=getgeom).values(
        'brgy_locat').annotate(counthigh=Count('brgy_locat'))
    print response

I was able to show all the values, but when using HttpResponse, it returns an empty set. What is the proper way of returning JSON data from a queryset? So far, tried this:

reference = FloodHazard.objects.filter(hazard='High')
ids = reference.values_list('id', flat=True)
response = {}
for myid in ids:
    getgeom = FloodHazard.objects.get(id=myid).geom
    response['high'] = BuildingStructure.objects.filter(geom__intersects=getgeom).values(
        'brgy_locat').annotate(counthigh=Count('brgy_locat'))

json_post = ujson.dumps(list(response))
return HttpResponse(json_post, content_type='application/json')

catavaran · Accepted Answer · 2015-03-11 03:11:37Z

1

There is no much sense in your code. You assign all querysets to the single key in the response dict. You should use a list for this purpose:

As far as I understand the code should be something like this:

response = []
for myid in ids:
    getgeom = FloodHazard.objects.get(id=myid).geom
    response.extend(BuildingStructure.objects.filter(geom__intersects=getgeom)
                                     .values('brgy_locat')
                                     .annotate(counthigh=Count('brgy_locat')))

json_post = ujson.dumps(response)

If you want to return a hazard level as well as the list of buildings then you can return a dict:

json_post = ujson.dumps({'hazard': 'high', 'buildings': response})

answered Mar 11, 2015 at 3:11

catavaran

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