Clean up field classes

rest_framework/fields.py

@@ -26,21 +26,88 @@ def is_simple_callable(obj):
 
 class Field(object):
     creation_counter = 0
-    default_validators = []
-    default_error_messages = {
-        'required': _('This field is required.'),
-        'invalid': _('Invalid value.'),
-    }
     empty = ''
 
-    def __init__(self, source=None, readonly=False, required=None,
-                 validators=[], error_messages=None):
+    def __init__(self, source=None):
         self.parent = None
 
         self.creation_counter = Field.creation_counter
         Field.creation_counter += 1
 
         self.source = source
+
+    def initialize(self, parent):
+        """
+        Called to set up a field prior to field_to_native or field_from_native.
+
+        parent - The parent serializer.
+        model_field - The model field this field corrosponds to, if one exists.
+        """
+        self.parent = parent
+        self.root = parent.root or parent
+        self.context = self.root.context
+
+    def field_from_native(self, data, field_name, into):
+        """
+        Given a dictionary and a field name, updates the dictionary `into`,
+        with the field and it's deserialized value.
+        """
+        return
+
+    def field_to_native(self, obj, field_name):
+        """
+        Given and object and a field name, returns the value that should be
+        serialized for that field.
+        """
+        if obj is None:
+            return self.empty
+
+        if self.source == '*':
+            return self.to_native(obj)
+
+        if self.source:
+            value = obj
+            for component in self.source.split('.'):
+                value = getattr(value, component)
+        else:
+            value = getattr(obj, field_name)
+        return self.to_native(value)
+
+    def to_native(self, value):
+        """
+        Converts the field's value into it's simple representation.
+        """
+        if is_simple_callable(value):
+            value = value()
+
+        if is_protected_type(value):
+            return value
+        elif hasattr(value, '__iter__') and not isinstance(value, (dict, basestring)):
+            return [self.to_native(item) for item in value]
+        return smart_unicode(value)
+
+    def attributes(self):
+        """
+        Returns a dictionary of attributes to be used when serializing to xml.
+        """
+        if getattr(self, 'type_name', None):
+            return {'type': self.type_name}
+        return {}
+
+
+class WritableField(Field):
+    """
+    Base for read/write fields.
+    """
+    default_validators = []
+    default_error_messages = {
+        'required': _('This field is required.'),
+        'invalid': _('Invalid value.'),
+    }
+
+    def __init__(self, source=None, readonly=False, required=None,
+                 validators=[], error_messages=None):
+        super(WritableField, self).__init__(source=source)
         self.readonly = readonly
         if required is None:
             self.required = not(readonly)
@@ -56,19 +123,6 @@ class Field(object):
 
         self.validators = self.default_validators + validators
 
-    def initialize(self, parent, model_field=None):
-        """
-        Called to set up a field prior to field_to_native or field_from_native.
-
-        parent - The parent serializer.
-        model_field - The model field this field corrosponds to, if one exists.
-        """
-        self.parent = parent
-        self.root = parent.root or parent
-        self.context = self.root.context
-        if model_field:
-            self.model_field = model_field
-
     def validate(self, value):
         if value in validators.EMPTY_VALUES and self.required:
             raise ValidationError(self.error_messages['required'])
@@ -117,96 +171,75 @@ class Field(object):
         """
         Reverts a simple representation back to the field's value.
         """
-        if hasattr(self, 'model_field'):
-            try:
-                return self.model_field.rel.to._meta.get_field(self.model_field.rel.field_name).to_python(value)
-            except:
-                return self.model_field.to_python(value)
         return value
 
-    def field_to_native(self, obj, field_name):
-        """
-        Given and object and a field name, returns the value that should be
-        serialized for that field.
-        """
-        if obj is None:
-            return self.empty
 
-        if self.source == '*':
-            return self.to_native(obj)
-
-        self.obj = obj  # Need to hang onto this in the case of model fields
-        if hasattr(self, 'model_field'):
-            return self.to_native(self.model_field._get_val_from_obj(obj))
-
-        if self.source:
-            value = obj
-            for component in self.source.split('.'):
-                value = getattr(value, component)
-        else:
-            value = getattr(obj, field_name)
-        return self.to_native(value)
+class ModelField(WritableField):
+    """
+    A generic field that can be used against an arbirtrary model field.
+    """
+    def __init__(self, *args, **kwargs):
+        try:
+            self.model_field = kwargs.pop('model_field')
+        except:
+            raise ValueError("ModelField requires 'model_field' kwarg")
+        super(ModelField, self).__init__(*args, **kwargs)
 
-    def to_native(self, value):
-        """
-        Converts the field's value into it's simple representation.
-        """
-        if is_simple_callable(value):
-            value = value()
+    def from_native(self, value):
+        try:
+            rel = self.model_field.rel
+        except:
+            return self.model_field.to_python(value)
+        return rel.to._meta.get_field(rel.field_name).to_python(value)
 
+    def field_to_native(self, obj, field_name):
+        value = self.model_field._get_val_from_obj(obj)
         if is_protected_type(value):
             return value
-        elif hasattr(self, 'model_field'):
-            return self.model_field.value_to_string(self.obj)
-        elif hasattr(value, '__iter__') and not isinstance(value, (dict, basestring)):
-            return [self.to_native(item) for item in value]
-        return smart_unicode(value)
+        return self.model_field.value_to_string(self.obj)
 
     def attributes(self):
-        """
-        Returns a dictionary of attributes to be used when serializing to xml.
-        """
-        try:
-            return {
-                "type": self.model_field.get_internal_type()
-            }
-        except AttributeError:
-            return {}
-
+        return {
+            "type": self.model_field.get_internal_type()
+        }
 
-class HyperlinkedIdentityField(Field):
-    def field_to_native(self, obj, field_name):
-        request = self.context.get('request', None)
-        view_name = self.parent.opts.view_name
-        view_kwargs = {'pk': obj.pk}
-        return reverse(view_name, kwargs=view_kwargs, request=request)
+##### Relational fields #####
 
 
-class RelatedField(Field):
+class RelatedField(WritableField):
     """
-    A base class for model related fields or related managers.
-
-    Subclass this and override `convert` to define custom behaviour when
-    serializing related objects.
+    Base class for related model fields.
     """
     def __init__(self, *args, **kwargs):
         self.queryset = kwargs.pop('queryset', None)
         super(RelatedField, self).__init__(*args, **kwargs)
 
     def field_to_native(self, obj, field_name):
-        obj = getattr(obj, self.source or field_name)
-        if obj.__class__.__name__ in ('RelatedManager', 'ManyRelatedManager'):
-            return [self.to_native(item) for item in obj.all()]
-        return self.to_native(obj)
+        value = getattr(obj, self.source or field_name)
+        return self.to_native(value)
 
-    def attributes(self):
+    def field_from_native(self, data, field_name, into):
+        value = data.get(field_name)
+        into[(self.source or field_name) + '_id'] = self.from_native(value)
+
+
+class ManyRelatedField(RelatedField):
+    """
+    Base class for related model managers.
+    """
+    def field_to_native(self, obj, field_name):
+        value = getattr(obj, self.source or field_name)
+        return [self.to_native(item) for item in value.all()]
+
+    def field_from_native(self, data, field_name, into):
         try:
-            return {
-                "rel": self.model_field.rel.__class__.__name__,
-                "to": smart_unicode(self.model_field.rel.to._meta)
-            }
-        except AttributeError:
-            return {}
+            value = data.getlist(self.source or field_name)
+        except:
+            value = data.get(self.source or field_name)
+        else:
+            if value == ['']:
+                value = []
+        into[field_name] = [self.from_native(item) for item in value]
 
 
 class PrimaryKeyRelatedField(RelatedField):
@@ -215,20 +248,11 @@ class PrimaryKeyRelatedField(RelatedField):
     """
 
     def to_native(self, pk):
-        """
-        You can subclass this method to provide different serialization
-        behavior based on the pk.
-        """
         return pk
 
     def field_to_native(self, obj, field_name):
-        # This is only implemented for performance reasons
-        #
-        # We could leave the default `RelatedField.field_to_native()` in place,
-        # and inside just implement `to_native()` as `return obj.pk`
-        #
-        # That would involve an extra database lookup.
         try:
+            # Prefer obj.serializable_value for performance reasons
             pk = obj.serializable_value(self.source or field_name)
         except AttributeError:
             # RelatedObject (reverse relationship)
@@ -237,18 +261,17 @@ class PrimaryKeyRelatedField(RelatedField):
         # Forward relationship
         return self.to_native(pk)
 
-    def field_from_native(self, data, field_name, into):
-        value = data.get(field_name)
-        into[field_name + '_id'] = self.from_native(value)
-
 
-class ManyPrimaryKeyRelatedField(PrimaryKeyRelatedField):
+class ManyPrimaryKeyRelatedField(ManyRelatedField):
     """
     Serializes a to-many related field or related manager to a pk value.
     """
+    def to_native(self, pk):
+        return pk
 
     def field_to_native(self, obj, field_name):
         try:
+            # Prefer obj.serializable_value for performance reasons
             queryset = obj.serializable_value(self.source or field_name)
         except AttributeError:
             # RelatedManager (reverse relationship)
@@ -257,40 +280,25 @@ class ManyPrimaryKeyRelatedField(PrimaryKeyRelatedField):
         # Forward relationship
         return [self.to_native(item.pk) for item in queryset.all()]
 
-    def field_from_native(self, data, field_name, into):
-        try:
-            value = data.getlist(field_name)
-        except:
-            value = data.get(field_name)
-        else:
-            if value == ['']:
-                value = []
-        into[field_name] = [self.from_native(item) for item in value]
-
 
-class NaturalKeyRelatedField(RelatedField):
+class HyperlinkedIdentityField(Field):
     """
-    Serializes a model related field or related manager to a natural key value.
+    A field that represents the model's identity using a hyperlink.
     """
-    is_natural_key = True  # XML renderer handles these differently
-
-    def to_native(self, obj):
-        if hasattr(obj, 'natural_key'):
-            return obj.natural_key()
-        return obj
+    def __init__(self, *args, **kwargs):
+        pass
 
-    def field_from_native(self, data, field_name, into):
-        value = data.get(field_name)
-        into[self.model_field.attname] = self.from_native(value)
+    def field_to_native(self, obj, field_name):
+        request = self.context.get('request', None)
+        view_name = self.parent.opts.view_name
+        view_kwargs = {'pk': obj.pk}
+        return reverse(view_name, kwargs=view_kwargs, request=request)
 
-    def from_native(self, value):
-        # TODO: Support 'using' : db = options.pop('using', DEFAULT_DB_ALIAS)
-        manager = self.model_field.rel.to._default_manager
-        manager = manager.db_manager(DEFAULT_DB_ALIAS)
-        return manager.get_by_natural_key(*value).pk
 
+##### Typed Fields #####
 
-class BooleanField(Field):
+class BooleanField(WritableField):
+    type_name = 'BooleanField'
     default_error_messages = {
         'invalid': _(u"'%s' value must be either True or False."),
     }
@@ -307,7 +315,9 @@ class BooleanField(Field):
         raise ValidationError(self.error_messages['invalid'] % value)
 
 
-class CharField(Field):
+class CharField(WritableField):
+    type_name = 'CharField'
+
     def __init__(self, max_length=None, min_length=None, *args, **kwargs):
         self.max_length, self.min_length = max_length, min_length
         super(CharField, self).__init__(*args, **kwargs)
@@ -323,6 +333,8 @@ class CharField(Field):
 
 
 class EmailField(CharField):
+    type_name = 'EmailField'
+
     default_error_messages = {
         'invalid': _('Enter a valid e-mail address.'),
     }
@@ -339,7 +351,9 @@ class EmailField(CharField):
         return result
 
 
-class DateField(Field):
+class DateField(WritableField):
+    type_name = 'DateField'
+
     default_error_messages = {
         'invalid': _(u"'%s' value has an invalid date format. It must be "
                      u"in YYYY-MM-DD format."),
@@ -373,7 +387,9 @@ class DateField(Field):
         raise ValidationError(msg)
 
 
-class DateTimeField(Field):
+class DateTimeField(WritableField):
+    type_name = 'DateTimeField'
+
     default_error_messages = {
         'invalid': _(u"'%s' value has an invalid format. It must be in "
                      u"YYYY-MM-DD HH:MM[:ss[.uuuuuu]][TZ] format."),
@@ -424,7 +440,9 @@ class DateTimeField(Field):
         raise ValidationError(msg)
 
 
-class IntegerField(Field):
+class IntegerField(WritableField):
+    type_name = 'IntegerField'
+
     default_error_messages = {
         'invalid': _('Enter a whole number.'),
         'max_value': _('Ensure this value is less than or equal to %(limit_value)s.'),
@@ -450,7 +468,9 @@ class IntegerField(Field):
         return value
 
 
-class FloatField(Field):
+class FloatField(WritableField):
+    type_name = 'FloatField'
+
     default_error_messages = {
         'invalid': _("'%s' value must be a float."),
     }

rest_framework/serializers.py

@@ -123,16 +123,8 @@ class BaseSerializer(Field):
         # Get the explicitly declared fields
         for key, field in self.fields.items():
             ret[key] = field
-            # Determine if the declared field corrosponds to a model field.
-            try:
-                if key == 'pk':
-                    model_field = obj._meta.pk
-                else:
-                    model_field = obj._meta.get_field_by_name(key)[0]
-            except:
-                model_field = None
             # Set up the field
-            field.initialize(parent=self, model_field=model_field)
+            field.initialize(parent=self)
 
         # Add in the default fields
         fields = self.default_fields(serialize, obj, data, nested)
@@ -157,12 +149,12 @@ class BaseSerializer(Field):
     #####
     # Field methods - used when the serializer class is itself used as a field.
 
-    def initialize(self, parent, model_field=None):
+    def initialize(self, parent):
         """
         Same behaviour as usual Field, except that we need to keep track
         of state so that we can deal with handling maximum depth and recursion.
         """
-        super(BaseSerializer, self).initialize(parent, model_field)
+        super(BaseSerializer, self).initialize(parent)
         self.stack = parent.stack[:]
         if parent.opts.nested and not isinstance(parent.opts.nested, bool):
             self.opts.nested = parent.opts.nested - 1
@@ -296,12 +288,22 @@ class ModelSerializerOptions(SerializerOptions):
         self.model = getattr(meta, 'model', None)
 
 
-class ModelSerializer(RelatedField, Serializer):
+class ModelSerializer(Serializer):
     """
     A serializer that deals with model instances and querysets.
     """
     _options_class = ModelSerializerOptions
 
+    def field_to_native(self, obj, field_name):
+        """
+        Override default so that we can apply ModelSerializer as a nested
+        field to relationships.
+        """
+        obj = getattr(obj, self.source or field_name)
+        if obj.__class__.__name__ in ('RelatedManager', 'ManyRelatedManager'):
+            return [self.to_native(item) for item in obj.all()]
+        return self.to_native(obj)
+
     def default_fields(self, serialize, obj=None, data=None, nested=False):
         """
         Return all the fields that should be serialized for the model.
@@ -330,7 +332,7 @@ class ModelSerializer(RelatedField, Serializer):
                 field = self.get_field(model_field)
 
             if field:
-                field.initialize(parent=self, model_field=model_field)
+                field.initialize(parent=self)
                 ret[model_field.name] = field
 
         return ret
@@ -339,7 +341,7 @@ class ModelSerializer(RelatedField, Serializer):
         """
         Returns a default instance of the pk field.
         """
-        return Field(readonly=True)
+        return Field()
 
     def get_nested_field(self, model_field):
         """
@@ -373,7 +375,7 @@ class ModelSerializer(RelatedField, Serializer):
         try:
             return field_mapping[model_field.__class__]()
         except KeyError:
-            return Field()
+            return ModelField(model_field=model_field)
 
     def restore_object(self, attrs, instance=None):
         """