From bef4408d102df061b4fe9352d8a7378ee22ff3ba Mon Sep 17 00:00:00 2001
From: Anton-Shutik <anton.shutik@itechart-group.com>
Date: Wed, 1 Jul 2015 14:43:18 +0300
Subject: [PATCH 1/5] Added MappingField

---
 rest_framework/fields.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 7960295bd..55fb2aac8 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1165,6 +1165,35 @@ class MultipleChoiceField(ChoiceField):
         ])
 
 
+# Mapping types...
+
+class MappingField(Field):
+    default_error_messages = {
+        'key_not_found': _('"{value}" not found in "mapping" dict'),
+        'value_not_found': _('"{value}" not found in "mapping" dict')
+    }
+
+    def __init__(self, mapping, **kwargs):
+        super(MappingField, self).__init__(**kwargs)
+
+        assert isinstance(mapping, dict), '"mapping" should be a dictionary'
+        for k, v in mapping.items():
+            assert isinstance(k, (str, int)) and isinstance(v, (str, int)), '"mapping" can contain only str or int'
+
+        self.mapping = mapping
+        self.reverse_mapping = {v: k for k, v in mapping.iteritems()}
+
+    def to_representation(self, value):
+        if value in self.mapping:
+            return self.mapping[value]
+        self.fail('key_not_found', value=value)
+
+    def to_internal_value(self, data):
+        if data in self.reverse_mapping:
+            return self.reverse_mapping[data]
+        self.fail('value_not_found', value=data)
+
+
 # File types...
 
 class FileField(Field):

From 806b0f60cf985ac26944d86b31f5a3211762182c Mon Sep 17 00:00:00 2001
From: Anton-Shutik <anton.shutik@itechart-group.com>
Date: Wed, 1 Jul 2015 14:43:35 +0300
Subject: [PATCH 2/5] Added test for MappingField

---
 tests/test_fields.py | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/tests/test_fields.py b/tests/test_fields.py
index 76e6d9d60..f4ef749aa 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -1125,6 +1125,38 @@ class TestMultipleChoiceField(FieldValues):
         assert field.get_value(QueryDict({})) == rest_framework.fields.empty
 
 
+# Mapping types...
+
+class TestMappingFieldWithIntKeys(FieldValues):
+    """
+    Valid and invalid values for `MappingField`.
+    """
+    valid_inputs = {
+        1: 'one',
+        2: 'two',
+        'three': 3,
+        'four': 4
+    }
+    invalid_inputs = {
+        5: ['"5" not found in "mapping" dict'],
+        'abc': ['"abc" not found in "mapping" dict']
+    }
+    outputs = {
+        'one': 1,
+        'two': 2,
+        3: 'three',
+        4: 'four'
+    }
+    field = serializers.MappingField(
+        mapping={
+            1: 'one',
+            2: 'two',
+            'three': 3,
+            'four': 4
+        }
+    )
+
+
 # File serializers...
 
 class MockFile:

From 643893334b6cde46274755f86da667068961df7d Mon Sep 17 00:00:00 2001
From: Anton-Shutik <anton.shutik@itechart-group.com>
Date: Wed, 1 Jul 2015 14:43:50 +0300
Subject: [PATCH 3/5] Added docs for MappingField

---
 docs/api-guide/fields.md | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/docs/api-guide/fields.md b/docs/api-guide/fields.md
index 18637f21c..b335a2b1a 100644
--- a/docs/api-guide/fields.md
+++ b/docs/api-guide/fields.md
@@ -364,6 +364,18 @@ As with `ChoiceField`, both the `allow_blank` and `allow_null` options are valid
 
 ---
 
+# Mapping field
+
+## MappingField
+
+A field that converts value with given mapping dict.
+
+    **Signature:** `MappingField(mapping)`
+
+- `mapping` - A dict of valid values that should be converted both directions.
+
+---
+
 # File upload fields
 
 #### Parsers and file uploads.

From 34232b01994c67b3e6c60a9102c7940caff81626 Mon Sep 17 00:00:00 2001
From: Anton-Shutik <anton.shutik@itechart-group.com>
Date: Wed, 1 Jul 2015 15:16:28 +0300
Subject: [PATCH 4/5] Changed MappingField default error messages

---
 rest_framework/fields.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 55fb2aac8..ff771128d 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1169,8 +1169,8 @@ class MultipleChoiceField(ChoiceField):
 
 class MappingField(Field):
     default_error_messages = {
-        'key_not_found': _('"{value}" not found in "mapping" dict'),
-        'value_not_found': _('"{value}" not found in "mapping" dict')
+        'key_not_found': _('"{value}" not found in "mapping" keys'),
+        'value_not_found': _('"{value}" not found in "mapping" values')
     }
 
     def __init__(self, mapping, **kwargs):

From 42dca62e7733bb095435b804061fbffe89f9de7a Mon Sep 17 00:00:00 2001
From: Anton-Shutik <anton.shutik@itechart-group.com>
Date: Wed, 1 Jul 2015 15:16:57 +0300
Subject: [PATCH 5/5] Fixed MappingField tests

---
 tests/test_fields.py | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/tests/test_fields.py b/tests/test_fields.py
index f4ef749aa..c13dc4c61 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -1132,21 +1132,21 @@ class TestMappingFieldWithIntKeys(FieldValues):
     Valid and invalid values for `MappingField`.
     """
     valid_inputs = {
-        1: 'one',
-        2: 'two',
-        'three': 3,
-        'four': 4
-    }
-    invalid_inputs = {
-        5: ['"5" not found in "mapping" dict'],
-        'abc': ['"abc" not found in "mapping" dict']
-    }
-    outputs = {
         'one': 1,
         'two': 2,
         3: 'three',
         4: 'four'
     }
+    invalid_inputs = {
+        5: ['"5" not found in "mapping" values'],
+        'abc': ['"abc" not found in "mapping" values']
+    }
+    outputs = {
+        1: 'one',
+        2: 'two',
+        'three': 3,
+        'four': 4
+    }
     field = serializers.MappingField(
         mapping={
             1: 'one',