From 82d4b2083292659358d5df4d03d2115576e8ae4e Mon Sep 17 00:00:00 2001
From: Timo Tuominen <tituomin@gmail.com>
Date: Mon, 1 Sep 2014 12:17:36 +0300
Subject: [PATCH 1/4] Add subclass matching to serializer field mapping.

---
 rest_framework/serializers.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index be8ad3f24..6d25161e2 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -907,6 +907,9 @@ class ModelSerializer(Serializer):
         try:
             return self.field_mapping[model_field.__class__](**kwargs)
         except KeyError:
+            for model_field_class, serializer_field_class in self.field_mapping.items():
+                if isinstance(model_field, model_field_class):
+                    return serializer_field_class(**kwargs)
             return ModelField(model_field=model_field, **kwargs)
 
     def get_validation_exclusions(self, instance=None):

From ae84b8b0e8a99261ea2436f77ab5238f21603c0c Mon Sep 17 00:00:00 2001
From: Timo Tuominen <tituomin@gmail.com>
Date: Mon, 1 Sep 2014 15:03:39 +0300
Subject: [PATCH 2/4] Traverse the method resolution order when mapping
 serializer fields.

---
 rest_framework/serializers.py | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 6d25161e2..f37fbf980 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -904,13 +904,11 @@ class ModelSerializer(Serializer):
             for attribute in attributes:
                 kwargs.update({attribute: getattr(model_field, attribute)})
 
-        try:
-            return self.field_mapping[model_field.__class__](**kwargs)
-        except KeyError:
-            for model_field_class, serializer_field_class in self.field_mapping.items():
-                if isinstance(model_field, model_field_class):
-                    return serializer_field_class(**kwargs)
-            return ModelField(model_field=model_field, **kwargs)
+        for model_field_baseclass in inspect.getmro(model_field.__class__):
+            serializer_field_class = self.field_mapping.get(model_field_baseclass)
+            if serializer_field_class:
+                return serializer_field_class(**kwargs)
+        return ModelField(model_field=model_field, **kwargs)
 
     def get_validation_exclusions(self, instance=None):
         """

From 582f6fdd4b0fb12a7c0d1fefe265499a284c9b79 Mon Sep 17 00:00:00 2001
From: Timo Tuominen <tituomin@gmail.com>
Date: Mon, 1 Sep 2014 15:54:33 +0300
Subject: [PATCH 3/4] Add utility function to match classes in dictionary.

---
 rest_framework/serializers.py | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index f37fbf980..5c33300c4 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -625,6 +625,21 @@ class ModelSerializerOptions(SerializerOptions):
         self.write_only_fields = getattr(meta, 'write_only_fields', ())
 
 
+def _get_class_mapping(mapping, obj):
+    """
+    Takes a dictionary with classes as keys, and an object.
+    Traverses the object's inheritance hierarchy in method
+    resolution order, and returns the first matching value
+    from the dictionary or None.
+
+    """
+    for baseclass in inspect.getmro(obj.__class__):
+        val = mapping.get(baseclass)
+        if val:
+            return val
+    return None
+
+
 class ModelSerializer(Serializer):
     """
     A serializer that deals with model instances and querysets.
@@ -899,15 +914,16 @@ class ModelSerializer(Serializer):
             models.URLField: ['max_length'],
         }
 
-        if model_field.__class__ in attribute_dict:
-            attributes = attribute_dict[model_field.__class__]
+        attributes = _get_class_mapping(attribute_dict, model_field)
+        if attributes:
             for attribute in attributes:
                 kwargs.update({attribute: getattr(model_field, attribute)})
 
-        for model_field_baseclass in inspect.getmro(model_field.__class__):
-            serializer_field_class = self.field_mapping.get(model_field_baseclass)
-            if serializer_field_class:
-                return serializer_field_class(**kwargs)
+        serializer_field_class = _get_class_mapping(
+            self.field_mapping, model_field)
+
+        if serializer_field_class:
+            return serializer_field_class(**kwargs)
         return ModelField(model_field=model_field, **kwargs)
 
     def get_validation_exclusions(self, instance=None):

From e437520217e20d500d641b95482d49484b1f24a7 Mon Sep 17 00:00:00 2001
From: Timo Tuominen <tituomin@gmail.com>
Date: Mon, 1 Sep 2014 17:02:48 +0300
Subject: [PATCH 4/4] Generator implementation of class mapping.

---
 rest_framework/serializers.py | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 5c33300c4..b3db35823 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -633,11 +633,10 @@ def _get_class_mapping(mapping, obj):
     from the dictionary or None.
 
     """
-    for baseclass in inspect.getmro(obj.__class__):
-        val = mapping.get(baseclass)
-        if val:
-            return val
-    return None
+    return next(
+        (mapping[cls] for cls in inspect.getmro(obj.__class__) if cls in mapping),
+        None
+    )
 
 
 class ModelSerializer(Serializer):