Clean up bind - no longer needs to be called multiple times in nested fields

rest_framework/fields.py

@@ -109,7 +109,8 @@ class Field(object):
     def __init__(self, read_only=False, write_only=False,
                  required=None, default=empty, initial=None, source=None,
                  label=None, help_text=None, style=None,
-                 error_messages=None, validators=[], allow_null=False):
+                 error_messages=None, validators=[], allow_null=False,
+                 context=None):
         self._creation_counter = Field._creation_counter
         Field._creation_counter += 1
 
@@ -135,6 +136,11 @@ class Field(object):
         self.validators = validators or self.default_validators[:]
         self.allow_null = allow_null
 
+        # These are set up by `.bind()` when the field is added to a serializer.
+        self.field_name = None
+        self.parent = None
+        self._context = {} if (context is None) else context
+
         # Collect default error message from self and parent classes
         messages = {}
         for cls in reversed(self.__class__.__mro__):
@@ -157,7 +163,14 @@ class Field(object):
         kwargs = copy.deepcopy(self._kwargs)
         return self.__class__(*args, **kwargs)
 
-    def bind(self, field_name, parent, root):
+    @property
+    def context(self):
+        root = self
+        while root.parent is not None:
+            root = root.parent
+        return root._context
+
+    def bind(self, field_name, parent):
         """
         Setup the context for the field instance.
         """
@@ -174,10 +187,8 @@ class Field(object):
 
         self.field_name = field_name
         self.parent = parent
-        self.root = root
-        self.context = parent.context
 
-        # `self.label` should deafult to being based on the field name.
+        # `self.label` should default to being based on the field name.
         if self.label is None:
             self.label = field_name.replace('_', ' ').capitalize()
 

rest_framework/relations.py

@@ -243,11 +243,6 @@ class ManyRelation(Field):
         assert child_relation is not None, '`child_relation` is a required argument.'
         super(ManyRelation, self).__init__(*args, **kwargs)
 
-    def bind(self, field_name, parent, root):
-        # ManyRelation needs to provide the current context to the child relation.
-        super(ManyRelation, self).bind(field_name, parent, root)
-        self.child_relation.bind(field_name, parent, root)
-
     def to_internal_value(self, data):
         return [
             self.child_relation.to_internal_value(item)

rest_framework/serializers.py

@@ -150,13 +150,20 @@ class SerializerMetaclass(type):
 
 
 class BindingDict(object):
+    """
+    This dict-like object is used to store fields on a serializer.
+
+    This ensures that whenever fields are added to the serializer we call
+    `field.bind()` so that the `field_name` and `parent` attributes
+    can be set correctly.
+    """
     def __init__(self, serializer):
         self.serializer = serializer
         self.fields = SortedDict()
 
     def __setitem__(self, key, field):
         self.fields[key] = field
-        field.bind(field_name=key, parent=self.serializer, root=self.serializer)
+        field.bind(field_name=key, parent=self.serializer)
 
     def __getitem__(self, key):
         return self.fields[key]
@@ -174,7 +181,6 @@ class BindingDict(object):
 @six.add_metaclass(SerializerMetaclass)
 class Serializer(BaseSerializer):
     def __init__(self, *args, **kwargs):
-        self.context = kwargs.pop('context', {})
         kwargs.pop('partial', None)
         kwargs.pop('many', None)
 
@@ -198,13 +204,6 @@ class Serializer(BaseSerializer):
     def _get_base_fields(self):
         return copy.deepcopy(self._declared_fields)
 
-    def bind(self, field_name, parent, root):
-        # If the serializer is used as a field then when it becomes bound
-        # it also needs to bind all its child fields.
-        super(Serializer, self).bind(field_name, parent, root)
-        for field_name, field in self.fields.items():
-            field.bind(field_name, self, root)
-
     def get_initial(self):
         return dict([
             (field.field_name, field.get_initial())
@@ -290,17 +289,10 @@ class ListSerializer(BaseSerializer):
         self.child = kwargs.pop('child', copy.deepcopy(self.child))
         assert self.child is not None, '`child` is a required argument.'
         assert not inspect.isclass(self.child), '`child` has not been instantiated.'
-        self.context = kwargs.pop('context', {})
         kwargs.pop('partial', None)
 
         super(ListSerializer, self).__init__(*args, **kwargs)
-        self.child.bind('', self, self)
+        self.child.bind(field_name='', parent=self)
-
-    def bind(self, field_name, parent, root):
-        # If the list is used as a field then it needs to provide
-        # the current context to the child serializer.
-        super(ListSerializer, self).bind(field_name, parent, root)
-        self.child.bind(field_name, self, root)
 
     def get_value(self, dictionary):
         # We override the default field access in order to support

tests/test_relations.py

@@ -51,7 +51,7 @@ class TestHyperlinkedIdentityField(APISimpleTestCase):
         self.instance = MockObject(pk=1, name='foo')
         self.field = serializers.HyperlinkedIdentityField(view_name='example')
         self.field.reverse = mock_reverse
-        self.field.context = {'request': True}
+        self.field._context = {'request': True}
 
     def test_representation(self):
         representation = self.field.to_representation(self.instance)
@@ -62,7 +62,7 @@ class TestHyperlinkedIdentityField(APISimpleTestCase):
         assert representation is None
 
     def test_representation_with_format(self):
-        self.field.context['format'] = 'xml'
+        self.field._context['format'] = 'xml'
         representation = self.field.to_representation(self.instance)
         assert representation == 'http://example.org/example/1.xml/'
 
@@ -91,14 +91,14 @@ class TestHyperlinkedIdentityFieldWithFormat(APISimpleTestCase):
         self.instance = MockObject(pk=1, name='foo')
         self.field = serializers.HyperlinkedIdentityField(view_name='example', format='json')
         self.field.reverse = mock_reverse
-        self.field.context = {'request': True}
+        self.field._context = {'request': True}
 
     def test_representation(self):
         representation = self.field.to_representation(self.instance)
         assert representation == 'http://example.org/example/1/'
 
     def test_representation_with_format(self):
-        self.field.context['format'] = 'xml'
+        self.field._context['format'] = 'xml'
         representation = self.field.to_representation(self.instance)
         assert representation == 'http://example.org/example/1.json/'