added slug support for HyperlinkedIdentityField

docs/api-guide/fields.md

@@ -280,5 +280,7 @@ This field is always read-only.
 
 * `view_name` - The view name that should be used as the target of the relationship.  **required**.
 * `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument.
+* `slug_field` - The field on the target that should be used for the lookup. Default is `'slug'`.
+* `slug_url_kwarg` - The named url parameter for the slug field lookup. Default is to use the same value as given for `slug_field`.
 
 [cite]: http://www.python.org/dev/peps/pep-0020/

rest_framework/fields.py

@@ -599,20 +599,50 @@ class HyperlinkedIdentityField(Field):
     """
     Represents the instance, or a property on the instance, using hyperlinking.
     """
+    pk_url_kwarg = 'pk'
+    slug_field = 'slug'
+    slug_url_kwarg = None  # Defaults to same as `slug_field` unless overridden
 
     def __init__(self, *args, **kwargs):
         # TODO: Make view_name mandatory, and have the
         # HyperlinkedModelSerializer set it on-the-fly
         self.view_name = kwargs.pop('view_name', None)
         self.format = kwargs.pop('format', None)
+
+        self.slug_field = kwargs.pop('slug_field', self.slug_field)
+        default_slug_kwarg = self.slug_url_kwarg or self.slug_field
+        self.slug_url_kwarg = kwargs.pop('slug_url_kwarg', default_slug_kwarg)
+
         super(HyperlinkedIdentityField, self).__init__(*args, **kwargs)
 
     def field_to_native(self, obj, field_name):
         request = self.context.get('request', None)
         format = self.format or self.context.get('format', None)
         view_name = self.view_name or self.parent.opts.view_name
-        view_kwargs = {'pk': obj.pk}
+        kwargs = {self.pk_url_kwarg: obj.pk}
-        return reverse(view_name, kwargs=view_kwargs, request=request, format=format)
+        try:
+            return reverse(view_name, kwargs=kwargs, request=request, format=format)
+        except:
+            pass
+
+        slug = getattr(obj, self.slug_field, None)
+
+        if not slug:
+            raise ValidationError('Could not resolve URL for field using view name "%s"' % view_name)
+
+        kwargs = {self.slug_url_kwarg: slug}
+        try:
+            return reverse(self.view_name, kwargs=kwargs, request=request, format=format)
+        except:
+            pass
+
+        kwargs = {self.pk_url_kwarg: obj.pk, self.slug_url_kwarg: slug}
+        try:
+            return reverse(self.view_name, kwargs=kwargs, request=request, format=format)
+        except:
+            pass
+
+        raise ValidationError('Could not resolve URL for field using view name "%s"', view_name)
 
 
 ##### Typed Fields #####