Get field name from serializer class

Author: Anton-Shutik

rest_framework_json_api/views.py

@@ -106,7 +106,6 @@ class RelatedMixin(object):
     This mixin handles all related entities, whose Serializers are declared in "related_serializers"
     """
     related_serializers = {}
-    field_name_mapping = {}
 
     def retrieve_related(self, request, *args, **kwargs):
         serializer_kwargs = {}
@@ -129,7 +128,7 @@ def retrieve_related(self, request, *args, **kwargs):
 
     def get_serializer_class(self):
         if 'related_field' in self.kwargs:
-            field_name = self.get_related_field_name()
+            field_name = self.kwargs['related_field']
             class_str = self.related_serializers.get(field_name, None)
             if class_str is None:
                 raise NotFound
@@ -138,8 +137,12 @@ def get_serializer_class(self):
 
     def get_related_field_name(self):
         field_name = self.kwargs['related_field']
-        if field_name in self.field_name_mapping:
-            return self.field_name_mapping[field_name]
+        # Making sure we're getting correct model field/property/method name
+        try:
+            return super(RelatedMixin, self).get_serializer_class()().fields[field_name].source
+        except KeyError:
+            # Looks like the field was not declared on the serializer
+            pass
         return field_name
 
     def get_related_instance(self):