Bit of extra tidying and plenty of docs

1 files changed, 33 insertions, 16 deletions

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 3029cf1c..0b0c2c9c 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -110,13 +110,15 @@ class BaseSerializer(Field):
     _dict_class = SortedDictWithMetadata
 
     def __init__(self, instance=None, data=None, files=None,
-                 context=None, partial=False, many=None, source=None):
+                 context=None, partial=False, many=None, source=None,
+                 allow_delete=False):
         super(BaseSerializer, self).__init__(source=source)
         self.opts = self._options_class(self.Meta)
         self.parent = None
         self.root = None
         self.partial = partial
         self.many = many
+        self.allow_delete = allow_delete
 
         self.context = context or {}
 
@@ -130,6 +132,12 @@ class BaseSerializer(Field):
         self._errors = None
         self._deleted = None
 
+        if many and instance is not None and not hasattr(instance, '__iter__'):
+            raise ValueError('instance should be a queryset or other iterable with many=True')
+
+        if allow_delete and not many:
+            raise ValueError('allow_delete should only be used for bulk updates, but you have not set many=True')
+
     #####
     # Methods to determine which fields to use when (de)serializing objects.
 
@@ -336,8 +344,15 @@ class BaseSerializer(Field):
         """
         This hook is required for bulk update.
         It is used to determine the canonical identity of a given object.
+
+        Note that the data has not been validated at this point, so we need
+        to make sure that we catch any cases of incorrect datatypes being
+        passed to this method.
         """
-        return data.get('id')
+        try:
+            return data.get('id', None)
+        except AttributeError:
+            return None
 
     @property
     def errors(self):
@@ -371,22 +386,12 @@ class BaseSerializer(Field):
                     identities = [self.get_identity(self.to_native(obj)) for obj in objects]
                     identity_to_objects = dict(zip(identities, objects))
 
-                try:
-                    iter(data)
-                    if isinstance(data, dict):
-                        raise TypeError
-                except TypeError:
-                    self._errors = {'non_field_errors': ['Expected a list of items']}
-                else:
+                if hasattr(data, '__iter__') and not isinstance(data, (dict, six.text_type)):
                     for item in data:
                         if update:
                             # Determine which object we're updating
-                            try:
-                                identity = self.get_identity(item)
-                            except:
-                                self.object = None
-                            else:
-                                self.object = identity_to_objects.pop(identity, None)
+                            identity = self.get_identity(item)
+                            self.object = identity_to_objects.pop(identity, None)
 
                         ret.append(self.from_native(item, None))
                         errors.append(self._errors)
@@ -395,6 +400,8 @@ class BaseSerializer(Field):
                         self._deleted = identity_to_objects.values()
 
                     self._errors = any(errors) and errors or []
+                else:
+                    self._errors = {'non_field_errors': ['Expected a list of items']}
             else:
                 ret = self.from_native(data, files)
 
@@ -445,7 +452,7 @@ class BaseSerializer(Field):
         else:
             self.save_object(self.object, **kwargs)
 
-        if self._deleted:
+        if self.allow_delete and self._deleted:
             [self.delete_object(item) for item in self._deleted]
 
         return self.object
@@ -736,3 +743,13 @@ class HyperlinkedModelSerializer(ModelSerializer):
             'many': to_many
         }
         return HyperlinkedRelatedField(**kwargs)
+
+    def get_identity(self, data):
+        """
+        This hook is required for bulk update.
+        We need to override the default, to use the url as the identity.
+        """
+        try:
+            return data.get('url', None)
+        except AttributeError:
+            return None