nested -> depth

docs/api-guide/serializers.md

@@ -107,21 +107,21 @@ where some of the attributes of an object might not be simple datatypes such as
 The `Serializer` class is itself a type of `Field`, and can be used to represent relationships where one object type is nested inside another.
 
     class UserSerializer(serializers.Serializer):
-        email = serializers.EmailField()
+        email = serializers.Field()
-        username = serializers.CharField()
+        username = serializers.Field()
-        
-        def restore_object(self, attrs, instance=None):
-            return User(**attrs)
-
 
     class CommentSerializer(serializers.Serializer):
         user = UserSerializer()
-        title = serializers.CharField()
+        title = serializers.Field()
-        content = serializers.CharField(max_length=200)
+        content = serializers.Field()
-        created = serializers.DateTimeField()
+        created = serializers.Field()
-        
+
-        def restore_object(self, attrs, instance=None):
+---
-            return Comment(**attrs)
+
+**Note**: Nested serializers are only suitable for read-only representations, as there are cases where they would have ambiguous or non-obvious behavior if used when updating instances.  For read-write representations you should always use a flat representation, by using one of the `RelatedField` subclasses.
+
+---
+
 
 ## Creating custom fields
 
@@ -225,40 +225,54 @@ For example:
 
 ## Specifiying nested serialization
 
-The default `ModelSerializer` uses primary keys for relationships, but you can also easily generate nested representations using the `nested` option:
+The default `ModelSerializer` uses primary keys for relationships, but you can also easily generate nested representations using the `depth` option:
 
     class AccountSerializer(serializers.ModelSerializer):
         class Meta:
             model = Account
             exclude = ('id',)
-            nested = True
+            depth = 1
 
-The `nested` option may be set to either `True`, `False`, or an integer value.  If given an integer value it indicates the depth of relationships that should be traversed before reverting to a flat representation.
+The `depth` option should be set to an integer value that indicates the depth of relationships that should be traversed before reverting to a flat representation.
 
-When serializing objects using a nested representation any occurances of recursion will be recognised, and will fall back to using a flat representation.
+## Customising the default fields
 
-## Customising the default fields used by a ModelSerializer
+You can create customized subclasses of `ModelSerializer` that use a different set of default fields for the representation, by overriding various `get_<field_type>_field` methods.
 
+Each of these methods may either return a field or serializer instance, or `None`.
 
+### get_pk_field
 
-    class AccountSerializer(serializers.ModelSerializer):
+**Signature**: `.get_pk_field(self, model_field)`
-        class Meta:
-            model = Account
 
+Returns the field instance that should be used to represent the pk field.
+
+### get_nested_field
+
+**Signature**: `.get_nested_field(self, model_field)`
+
+Returns the field instance that should be used to represent a related field when `depth` is specified as being non-zero.
+
+### get_related_field
+
+**Signature**: `.get_related_field(self, model_field, to_many=False)`
+
+Returns the field instance that should be used to represent a related field when `depth` is not specified, or when nested representations are being used and the depth reaches zero.
+
+### get_field
+
+**Signature**: `.get_field(self, model_field)`
+
+Returns the field instance that should be used for non-relational, non-pk fields.
+
+### Example:
+
+The following custom model serializer could be used as a base class for model serializers that should always exclude the pk by default.
+
+    class NoPKModelSerializer(serializers.ModelSerializer):
         def get_pk_field(self, model_field):
-            return serializers.Field(read_only=True)
+            return None
 
-        def get_nested_field(self, model_field):
-            return serializers.ModelSerializer()
-
-        def get_related_field(self, model_field, to_many=False):
-            queryset = model_field.rel.to._default_manager
-            if to_many:
-                return serializers.ManyRelatedField(queryset=queryset)
-            return serializers.RelatedField(queryset=queryset)
-
-        def get_field(self, model_field):
-            return serializers.ModelField(model_field=model_field)
 
 
 [cite]: https://groups.google.com/d/topic/django-users/sVFaOfQi4wY/discussion

rest_framework/serializers.py

@@ -74,7 +74,7 @@ class SerializerOptions(object):
     Meta class options for Serializer
     """
     def __init__(self, meta):
-        self.nested = getattr(meta, 'nested', False)
+        self.depth = getattr(meta, 'depth', 0)
         self.fields = getattr(meta, 'fields', ())
         self.exclude = getattr(meta, 'exclude', ())
 
@@ -156,10 +156,8 @@ class BaseSerializer(Field):
         """
         super(BaseSerializer, self).initialize(parent)
         self.stack = parent.stack[:]
-        if parent.opts.nested and not isinstance(parent.opts.nested, bool):
+        if parent.opts.depth:
-            self.opts.nested = parent.opts.nested - 1
+            self.opts.depth = parent.opts.depth - 1
-        else:
-            self.opts.nested = parent.opts.nested
 
     #####
     # Methods to convert or revert from objects <--> primative representations.
@@ -182,14 +180,10 @@ class BaseSerializer(Field):
         ret = self._dict_class()
         ret.fields = {}
 
-        fields = self.get_fields(serialize=True, obj=obj, nested=self.opts.nested)
+        fields = self.get_fields(serialize=True, obj=obj, nested=bool(self.opts.depth))
         for field_name, field in fields.items():
             key = self.get_field_key(field_name)
-            try:
+            value = field.field_to_native(obj, field_name)
-                value = field.field_to_native(obj, field_name)
-            except RecursionOccured:
-                field = self.get_fields(serialize=True, obj=obj, nested=False)[field_name]
-                value = field.field_to_native(obj, field_name)
             ret[key] = value
             ret.fields[key] = field
         return ret
@@ -199,7 +193,7 @@ class BaseSerializer(Field):
         Core of deserialization, together with `restore_object`.
         Converts a dictionary of data into a dictionary of deserialized fields.
         """
-        fields = self.get_fields(serialize=False, data=data, nested=self.opts.nested)
+        fields = self.get_fields(serialize=False, data=data, nested=bool(self.opts.depth))
         reverted_data = {}
         for field_name, field in fields.items():
             try:
@@ -213,7 +207,8 @@ class BaseSerializer(Field):
         """
         Run `validate_<fieldname>()` and `validate()` methods on the serializer
         """
-        fields = self.get_fields(serialize=False, data=attrs, nested=self.opts.nested)
+        # TODO: refactor this so we're not determining the fields again
+        fields = self.get_fields(serialize=False, data=attrs, nested=bool(self.opts.depth))
 
         for field_name, field in fields.items():
             try: