use_value feature added to ChoiceField

docs/api-guide/fields.md

@@ -366,6 +366,7 @@ Used by `ModelSerializer` to automatically generate fields if the corresponding
 - `allow_blank` - If set to `True` then the empty string should be considered a valid value. If set to `False` then the empty string is considered invalid and will raise a validation error. Defaults to `False`.
 - `html_cutoff` - If set this will be the maximum number of choices that will be displayed by a HTML select drop down. Can be used to ensure that automatically generated ChoiceFields with very large possible selections do not prevent a template from rendering. Defaults to `None`.
 - `html_cutoff_text` - If set this will display a textual indicator if the maximum number of items have been cutoff in an HTML select drop down. Defaults to `"More than {count} items…"`
+- `use_value` - If set to `True` then input and output values changed with choice field values.
 
 Both the `allow_blank` and `allow_null` are valid options on `ChoiceField`, although it is highly recommended that you only use one and not both. `allow_blank` should be preferred for textual choices, and `allow_null` should be preferred for numeric or other non-textual choices.
 

rest_framework/fields.py

@@ -1245,12 +1245,23 @@ class ChoiceField(Field):
         self.choices = flatten_choices_dict(self.grouped_choices)
         self.html_cutoff = kwargs.pop('html_cutoff', self.html_cutoff)
         self.html_cutoff_text = kwargs.pop('html_cutoff_text', self.html_cutoff_text)
+        self.use_value = kwargs.pop("use_value", False)
 
         # Map the string representation of choices to the underlying value.
         # Allows us to deal with eg. integer choices while supporting either
         # integer or string input, but still get the correct datatype out.
-        self.choice_strings_to_values = {
+
-            six.text_type(key): key for key in self.choices.keys()
+        if self.use_value:
+            self.choice_strings_to_values = {
+                six.text_type(value): key for key, value in self.choices.items()
+            }
+        else:
+            self.choice_strings_to_values = {
+                six.text_type(key): key for key in self.choices.keys()
+            }
+
+        self.choice_values_to_strings = {
+            six.text_type(key): value for key, value in self.choices.items()
         }
 
         self.allow_blank = kwargs.pop('allow_blank', False)
@@ -1269,6 +1280,8 @@ class ChoiceField(Field):
     def to_representation(self, value):
         if value in ('', None):
             return value
+        if self.use_value:
+            return self.choice_values_to_strings.get(six.text_type(value), value)
         return self.choice_strings_to_values.get(six.text_type(value), value)
 
     def iter_options(self):

tests/test_fields.py

@@ -1212,6 +1212,31 @@ class TestChoiceFieldWithType(FieldValues):
     )
 
 
+class TestChoiceFieldWithUseDone(FieldValues):
+    """
+    Valid and invalid values for a `Choice` field that uses an integer type,
+    instead of a char type.
+    """
+    valid_inputs = {
+        'seller': 1,
+        'client': 2,
+    }
+    invalid_inputs = {
+        "2": ['"2" is not a valid choice.']
+    }
+    outputs = {
+        '1': 'seller',
+        2: 'client'
+    }
+    field = serializers.ChoiceField(
+        choices=[
+            (1, 'seller'),
+            (2, 'client')
+        ],
+        use_value=True
+    )
+
+
 class TestChoiceFieldWithListChoices(FieldValues):
     """
     Valid and invalid values for a `Choice` field that uses a flat list for the