refactor: Move flattening to serializer base class

people/serializers.py

@@ -2,11 +2,69 @@
 Serialize models to and deserialize from JSON.
 """
 
+from collections import OrderedDict
+import typing
+
 from rest_framework import serializers
 
 from . import models
 
 
+class FlattenedModelSerializer(serializers.ModelSerializer):
+    @classmethod
+    def flatten_data(cls, data,
+                     sub_type: typing.Type = dict,
+                     sub_value_accessor: typing.Callable = lambda x: x.items()) -> typing.OrderedDict:
+        """
+        Flatten a dictionary so that subdictionaries become a series of `key[.subkey[.subsubkey ...]]` entries
+        in the top level dictionary.
+
+        Works for other data structures (e.g. DRF Serializers) by providing suitable values for the
+        `sub_type` and `sub_value_accessor` parameters.
+
+        :param data: Dictionary or other data structure to flatten
+        :param sub_type: Type to recursively flatten
+        :param sub_value_accessor: Function to access keys and values contained within sub_type.
+        """
+        data_out = OrderedDict()
+
+        for key, value in sub_value_accessor(data):
+            if isinstance(value, sub_type):
+                # Recursively flatten nested structures of type `sub_type`
+                sub_flattened = cls.flatten_data(value,
+                                                 sub_type=sub_type,
+                                                 sub_value_accessor=sub_value_accessor).items()
+
+                # Enter recursively flattened values into result dictionary
+                for sub_key, sub_value in sub_flattened:
+                    # Keys in result dictionary are of format `key[.subkey[.subsubkey ...]]`
+                    data_out[f'{key}.{sub_key}'] = sub_value
+
+            else:
+                data_out[key] = value
+
+        return data_out
+    
+    @property
+    def column_headers(self) -> typing.Collection:
+        """
+        Get all column headers that will be output by this serializer.
+        """
+        return self.flatten_data(self.fields,
+                                 sub_type=serializers.BaseSerializer,
+                                 sub_value_accessor=lambda x: x.fields.items())
+
+    def to_representation(self, instance) -> typing.OrderedDict:
+        """
+        
+        """
+        rep = super().to_representation(instance)
+        
+        rep = self.flatten_data(rep)
+
+        return rep
+
+
 class PersonSerializer(serializers.ModelSerializer):
     class Meta:
         model = models.Person
@@ -30,7 +88,7 @@ class PersonExportSerializer(serializers.ModelSerializer):
         ]
 
         
-class RelationshipSerializer(serializers.ModelSerializer):
+class RelationshipSerializer(FlattenedModelSerializer):
     source = PersonSerializer()
     target = PersonSerializer()
 
@@ -41,3 +99,15 @@ class RelationshipSerializer(serializers.ModelSerializer):
             'source',
             'target',
         ]
+        
+    def to_representation(self, instance):
+        rep = super().to_representation(instance)
+
+        # try:
+        #     for answer in instance.current_answers.question_answers.all():
+        #         rep[answer.question.text] = answer.text
+        #
+        # except AttributeError:
+        #     pass
+
+        return rep

people/views/export.py

@@ -5,8 +5,6 @@ from django.contrib.auth.mixins import LoginRequiredMixin
 from django.http import HttpResponse
 from django.views.generic.list import BaseListView
 
-from rest_framework.serializers import BaseSerializer
-
 from .. import models, serializers
 
 
@@ -14,55 +12,16 @@ class CsvExportView(LoginRequiredMixin, BaseListView):
     model = None
     serializer_class = None
 
-    @classmethod
-    def flatten_data(cls, data,
-                     sub_type: typing.Type = dict,
-                     sub_value_accessor: typing.Callable = lambda x: x.items()) -> typing.Dict:
-        """
-        Flatten a dictionary so that subdictionaryies become a series of `key[.subkey[.subsubkey ...]]` entries
-        in the top level dictionary.
-
-        Works for other data structures (e.g. DRF Serializers) by providing suitable values for the
-        `sub_type` and `sub_value_accessor` parameters.
-
-        :param data: Dictionary or other data structure to flatten
-        :param sub_type: Type to recursively flatten
-        :param sub_value_accessor: Function to access keys and values contained within sub_type.
-        """
-        data_out = {}
-
-        for key, value in sub_value_accessor(data):
-            if isinstance(value, sub_type):
-                # Recursively flatten nested structures of type `sub_type`
-                sub_flattened = cls.flatten_data(value,
-                                                 sub_type=sub_type,
-                                                 sub_value_accessor=sub_value_accessor).items()
-
-                # Enter recursively flattened values into result dictionary
-                for sub_key, sub_value in sub_flattened:
-                    # Keys in result dictionary are of format `key[.subkey[.subsubkey ...]]`
-                    data_out[f'{key}.{sub_key}'] = sub_value
-                    
-            else:
-                data_out[key] = value
-
-        return data_out
-
     def render_to_response(self, context: typing.Dict) -> HttpResponse:
         response = HttpResponse(content_type='text/csv')
         response['Content-Disposition'] = f'attachment; filename="{self.get_context_object_name(self.object_list)}.csv"'
         
         serializer = self.serializer_class(self.get_queryset(), many=True)
-        columns = self.flatten_data(serializer.child.fields,
-                                    sub_type=BaseSerializer,
-                                    sub_value_accessor=lambda x: x.fields.items())
-        
-        writer = csv.DictWriter(response, fieldnames=columns)
+
+        writer = csv.DictWriter(response, fieldnames=serializer.child.column_headers)
         writer.writeheader()
+        writer.writerows(serializer.data)
         
-        for row in serializer.data:
-            writer.writerow(self.flatten_data(row))
-            
         return response