Refactor setup method as lazy evaluation in the form field

Author: Ryan P Kilby

rest_framework_filters/filters.py

@@ -22,7 +22,6 @@ def _import_class(path):
 class RelatedFilter(ModelChoiceFilter):
     def __init__(self, filterset, *args, **kwargs):
         self.filterset = filterset
-        # self.parent_relation = kwargs.get('parent_relation', None)
         return super(RelatedFilter, self).__init__(*args, **kwargs)
 
     def filterset():
@@ -58,8 +57,11 @@ class FilterSetSubset(BaseFilterSet):
 
         return FilterSetSubset
 
-    def setup_filterset(self):
-        self.extra['queryset'] = self.filterset._meta.model.objects.all()
+    @property
+    def field(self):
+        # if no queryset is provided, default to the filterset's default queryset
+        self.extra.setdefault('queryset', self.filterset._meta.model._default_manager.all())
+        return super(RelatedFilter, self).field
 
 
 class AllLookupsFilter(Filter):

rest_framework_filters/filterset.py

@@ -66,8 +66,6 @@ def __init__(self, *args, **kwargs):
 
         for name, filter_ in six.iteritems(self.filters.copy()):
             if isinstance(filter_, filters.RelatedFilter):
-                filter_.setup_filterset()
-
                 # Add an 'isnull' filter to allow checking if the relation is empty.
                 filter_name = "%s%sisnull" % (filter_.name, LOOKUP_SEP)
                 if filter_name not in self.filters: