Merge 9eba60f5b0 into f1251e8c58

docs/api-guide/fields.md

@@ -20,7 +20,7 @@ Each serializer field class constructor takes at least these arguments.  Some Fi
 
 ### `source`
 
-The name of the attribute that will be used to populate the field.  May be a method that only takes a `self` argument, such as `Field(source='get_absolute_url')`, or may use dotted notation to traverse attributes, such as `Field(source='user.email')`.
+The name of the attribute that will be used to populate the field.  May be a method that only takes a `self` argument, such as `Field(source='get_absolute_url')`, or may use dotted notation to traverse attributes, such as `Field(source='user.email')`. Alternatively, `source` can be a callable that takes a single argument (the object being serialized) and returns the value that will populate this field.
 
 The value `source='*'` has a special meaning, and is used to indicate that the entire object should be passed through to the field.  This can be useful for creating nested representations.  (See the implementation of the `PaginationSerializer` class for an example.)
 

rest_framework/fields.py

@@ -160,6 +160,9 @@ class Field(object):
         source = self.source or field_name
         value = obj
 
+        if callable(source):
+            return source(value)
+
         for component in source.split('.'):
             value = get_component(value, component)
             if value is None:

rest_framework/tests/test_serializer.py

@@ -803,6 +803,26 @@ class CallableDefaultValueTests(TestCase):
         self.assertEqual(instance.text, 'overridden')
 
 
+class CallableSourceTests(TestCase):
+    def setUp(self):
+        class CommentSerializer(serializers.Serializer):
+            email = serializers.EmailField()
+            content = serializers.CharField(max_length=1000)
+            length = serializers.IntegerField(
+                source=lambda comment: len(comment.content),
+                read_only=True)
+        self.serializer_class = CommentSerializer
+
+    def test_callable_source(self):
+        instance = Comment('user@email.com', 'foobar', None)
+        serializer = self.serializer_class(instance=instance)
+        self.assertEquals(serializer.data, {
+            'email': 'user@email.com',
+            'content': 'foobar',
+            'length': 6
+        })
+
+
 class ManyRelatedTests(TestCase):
     def test_reverse_relations(self):
         post = BlogPost.objects.create(title="Test blog post")