django-rest-framework/rest_framework/utils/serializer_helpers.py

import collections
from rest_framework.compat import OrderedDict


class ReturnDict(OrderedDict):
    """
    Return object from `serialier.data` for the `Serializer` class.
    Includes a backlink to the serializer instance for renderers
    to use if they need richer field information.
    """
    def __init__(self, *args, **kwargs):
        self.serializer = kwargs.pop('serializer')
        super(ReturnDict, self).__init__(*args, **kwargs)

    def copy(self):
        return ReturnDict(self, serializer=self.serializer)


class ReturnList(list):
    """
    Return object from `serialier.data` for the `SerializerList` class.
    Includes a backlink to the serializer instance for renderers
    to use if they need richer field information.
    """
    def __init__(self, *args, **kwargs):
        self.serializer = kwargs.pop('serializer')
        super(ReturnList, self).__init__(*args, **kwargs)


class BoundField(object):
    """
    A field object that also includes `.value` and `.error` properties.
    Returned when iterating over a serializer instance,
    providing an API similar to Django forms and form fields.
    """
    def __init__(self, field, value, errors, prefix=''):
        self._field = field
        self.value = value
        self.errors = errors
        self.name = prefix + self.field_name

    def __getattr__(self, attr_name):
        return getattr(self._field, attr_name)

    @property
    def _proxy_class(self):
        return self._field.__class__

    def __repr__(self):
        return '<%s value=%s errors=%s>' % (
            self.__class__.__name__, self.value, self.errors
        )


class NestedBoundField(BoundField):
    """
    This `BoundField` additionally implements __iter__ and __getitem__
    in order to support nested bound fields. This class is the type of
    `BoundField` that is used for serializer fields.
    """
    def __iter__(self):
        for field in self.fields.values():
            yield self[field.field_name]

    def __getitem__(self, key):
        field = self.fields[key]
        value = self.value.get(key) if self.value else None
        error = self.errors.get(key) if self.errors else None
        if hasattr(field, 'fields'):
            return NestedBoundField(field, value, error, prefix=self.name + '.')
        return BoundField(field, value, error, prefix=self.name + '.')


class BindingDict(collections.MutableMapping):
    """
    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 = OrderedDict()

    def __setitem__(self, key, field):
        self.fields[key] = field
        field.bind(field_name=key, parent=self.serializer)

    def __getitem__(self, key):
        return self.fields[key]

    def __delitem__(self, key):
        del self.fields[key]

    def __iter__(self):
        return iter(self.fields)

    def __len__(self):
        return len(self.fields)