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# Copyright 2009 10gen, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Manipulators that can edit SON objects as they enter and exit a database.
New manipulators should be defined as subclasses of SONManipulator and can be
installed on a database by calling `pymongo.database.Database.add_son_manipulator`."""
from objectid import ObjectId
from son import SON
class SONManipulator(object):
"""A base son manipulator.
This manipulator just saves and restores objects without changing them.
"""
def __init__(self, database):
"""Instantiate the manager.
:Parameters:
- `database`: a Mongo Database
"""
self.__database = database
def transform_incoming(self, son, collection):
"""Manipulate an incoming son object.
:Parameters:
- `son`: the son object to be inserted into the database
- `collection`: the collection the object is being inserted into
"""
return son
def transform_outgoing(self, son, collection):
"""Manipulate an outgoing son object.
:Parameters:
- `son`: the son object being retrieved from the database
- `collection`: the collection this object was stored in
"""
return son
class ObjectIdInjector(SONManipulator):
"""A son manipulator that adds the _id field if it is missing.
"""
def transform_incoming(self, son, collection):
"""Add an _id field if it is missing.
"""
if not "_id" in son:
son["_id"] = ObjectId()
return son
class ObjectIdShuffler(SONManipulator):
"""A son manipulator that moves _id to the first position.
"""
def transform_incoming(self, son, collection):
"""Move _id to the front if it's there.
"""
if not "_id" in son:
return son
transformed = SON({"_id": son["_id"]})
transformed.update(son)
return transformed
class NamespaceInjector(SONManipulator):
"""A son manipulator that adds the _ns field.
"""
def transform_incoming(self, son, collection):
"""Add the _ns field to the incoming object
"""
son["_ns"] = collection.name()
return son
# TODO make a generic translator for custom types. Take encode, decode,
# should_encode and should_decode functions and just encode and decode where
# necessary. See examples/custom_type.py for where this would be useful.
# Alternatively it could take a should_encode, to_binary, from_binary and
# binary subtype.
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