Add SerializerMethodField

2 files changed, 48 insertions, 0 deletions

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index c68c39b5..d1e9c45d 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1019,3 +1019,17 @@ class ImageField(FileField):
         if hasattr(f, 'seek') and callable(f.seek):
             f.seek(0)
         return f
+
+
+class SerializerMethodField(Field):
+    """
+    A field that gets its value by calling a method on the serializer it's attached to.
+    """
+
+    def __init__(self, method_name):
+        self.method_name = method_name
+        super(SerializerMethodField, self).__init__()
+
+    def field_to_native(self, obj, field_name):
+        value = getattr(self.parent, self.method_name)(obj)
+        return self.to_native(value)
diff --git a/rest_framework/tests/serializer.py b/rest_framework/tests/serializer.py
index fb1be7eb..cc6e9d5c 100644
--- a/rest_framework/tests/serializer.py
+++ b/rest_framework/tests/serializer.py
@@ -497,6 +497,40 @@ class ManyRelatedTests(TestCase):
         self.assertEqual(serializer.data, expected)
 
 
+class SerializerMethodFieldTests(TestCase):
+    def setUp(self):
+
+        class BoopSerializer(serializers.Serializer):
+            beep = serializers.SerializerMethodField('get_beep')
+            boop = serializers.Field()
+            boop_count = serializers.SerializerMethodField('get_boop_count')
+
+            def get_beep(self, obj):
+                return 'hello!'
+
+            def get_boop_count(self, obj):
+                return len(obj.boop)
+
+        self.serializer_class = BoopSerializer
+
+    def test_serializer_method_field(self):
+
+        class MyModel(object):
+            boop = ['a', 'b', 'c']
+
+        source_data = MyModel()
+
+        serializer = self.serializer_class(source_data)
+
+        expected = {
+            'beep': u'hello!',
+            'boop': [u'a', u'b', u'c'],
+            'boop_count': 3,
+        }
+
+        self.assertEqual(serializer.data, expected)
+
+
 # Test for issue #324
 class BlankFieldTests(TestCase):
     def setUp(self):