`Tastypie BaseResource to build lists from a queryset` Many to Many relationships in Tastypie Resources require a Manager (9.12 - 9.14), but if you are using a queryset, you can't use the relationship. This base resource allows you to extend your Resources to easily build a pseudo ToMany relationship from your queryset. Special thanks to https:/…

models.py

# how the models are related
# track -- generic --> audioclips <-- sample

class SampledTracksManager(models.Manager):

    def get_track_samples(self, instance):
                
        # must iterate through list because Audioclip object is unscriptable
        audioclip_ids = []
        for audioclip in instance.audioclips.all():
            audioclip_ids.append(audioclip.id)
        
        # return custom queryset where audioclip_id exists in audioclip_ids built from Track model
        return Sample.objects.filter(audioclip_id__in=audioclip_ids)

class Track(models.Model):
    
    objects = SampledTracksManager()
    
    # ... model properties ...
    
    audioclips = generic.GenericRelation('Audioclip', object_id_field="medium_id", content_type_field="medium_type")
        
    def __unicode__(self):
        return "%s" % (self.title)
    
    def get_track_samples(self):
        return Track.objects.get_track_samples(self)

resources.py

class ResolverResource(ModelResource):
    def get_reverse_kwargs(self, resolver_type, resource_name=None, resource_id=None, detail_uri_name='pk'):
        """
        Return a dictionary of named URLs included in Tastypie by default.
        These can be found in tastypie.resources.Resource.base_urls. They
        are included here as a convenience and a form of documentation.
 
        By using this method we can use reverse URL resolution and
        automatically have all of the kwargs needed by
        django.core.urlresolvers.reverse to return the URL string.
 
        """
        
        if resource_name is None:
            resource_name = self._meta.resource_name        
        
        kwargs = {
            'api_dispatch_list': {
                'resource_name': resource_name,
                'api_name': self.api_name
            },
            'api_get_schema': {
                'resource_name': resource_name,
                'api_name': self.api_name
            },
            'api_get_multiple': {
                'resource_name': resource_name,
                '%s_list' % (detail_uri_name) : resource_id,
                'api_name': self.api_name
            },
            'api_dispatch_detail': {
                'resource_name' : resource_name,
                '%s' % (detail_uri_name) : resource_id,
                'api_name' : self.api_name
            }
        }
        
        return kwargs[resolver_type]
    
    def get_reverse_uri(self, resolver_type, resource_name=None, resource_id=None):
        kwargs = self.get_reverse_kwargs(resolver_type, resource_name, resource_id)
        return reverse(resolver_type, kwargs=kwargs)

    def get_uri_set(self, ids, resource_name=None):
        # TODO build a ; delimited string from ids (EG: 1;2;3) and look up 'api_get_multiple'
        pass

        
    def get_uri_list(self, ids, resource_name=None):
        
        uri_list = []
        for id in ids:
            uri = self.get_reverse_uri('api_dispatch_detail', resource_name, id)
            uri_list.append(uri)
        
        return uri_list
 
 
class TrackResource(ResolverResource):
    
    album_id = fields.ToOneField('samped.api.resources.AlbumResource', 'album')
    label_id = fields.ToOneField('samped.api.resources.LabelResource', 'label')
    artists = fields.ToManyField('samped.api.resources.ArtistResource', 'artists')
 
    
    # have to build uri list from queryset
    # because tastypie m2m expects a Manager, but querysets for custom querys will crash 
#    track_samples = fields.ToManyField('samped.api.resources.SampleResource', 'get_track_samples')
    
    def dehydrate(self, bundle):
        
        # have to build uri list from queryset
        # because tastypie m2m expects a Manager, but querysets for custom querys will crash 
        sample_ids = Track.objects.get_track_samples(bundle.obj).values_list('id', flat=True)

        # sample_ids = [1, 23, 56]
        bundle.data['track_samples'] = self.get_uri_list(sample_ids, 'sample')
        
        # bundle.data['track_samples'] = ['/api/v1/sample/1/', '/api/v1/sample/23/', '/api/v1/sample/56/']

        return bundle
    
    class Meta:
        queryset = Track.objects.all()