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Marshmallow multiplexing schema

Project Description
=====================
Marshmallow-OneOfSchema
=====================

.. image:: https://travis-ci.org/maximkulkin/marshmallow-oneofschema.svg?branch=master
:target: https://travis-ci.org/maximkulkin/marshmallow-oneofschema
:alt: Build Status

An extenstion to Marshmallow to support schema (de)multiplexing.

Marshmallow is a fantastic library for serialization and deserialization of data.
For more on that project see its `GitHub <https://github.com/marshmallow-code/marshmallow>`_
page or its `Documentation <http://marshmallow.readthedocs.org/en/latest/>`_.

This library adds a special kind of schema that actually multiplexes other schemas
based on object type. When serializing values, it uses get_obj_type() method
to get object type name. Then it uses `type_schemas` name-to-Schema mapping
to get schema for that particular object type, serializes object using that
schema and adds an extra field with name of object type. Deserialization is reverse.

Installing
----------
::

$ pip install marshmallow-oneofschema

Importing
---------
Here is how to import the necessary field class
::

from marshmallow_oneofschema import OneOfSchema

Example
-------

The code below demonstrates how to setup a schema with a PolyField. For the full context check out the tests.
Once setup the schema should act like any other schema. If it does not then please file an Issue.

.. code:: python

import marshmallow
import marshmallow.fields
from marshmallow_oneofschema import OneOfSchema

class Foo(object):
def __init__(self, foo):
self.foo = foo

class Bar(object):
def __init__(self, bar):
self.bar = bar

class FooSchema(marshmallow.Schema):
foo = marshmallow.fields.String(required=True)

@marshmallow.post_load
def make_foo(self, data):
return Foo(**data)

class BarSchema(marshmallow.Schema):
bar = marshmallow.fields.Integer(required=True)

@marshmallow.post_load
def make_bar(self, data):
return Bar(**data)

class MyUberSchema(OneOfSchema):
type_schemas = {
'foo': FooSchema,
'bar': BarSchema,
}

def get_obj_type(self, obj):
if isinstance(obj, Foo):
return 'foo'
elif isinstance(obj, Bar):
return 'bar'
else:
raise Exception('Unknown object type: %s' % obj.__class__.__name__)

MyUberSchema().dump([Foo(foo='hello'), Bar(bar=123)], many=True).data
# => [{'type': 'foo', 'foo': 'hello'}, {'type': 'bar', 'bar': 123}]

MyUberSchema().load([{'type': 'foo', 'foo': 'hello'}, {'type': 'bar', 'bar': 123}]).data
# => [Foo('hello'), Bar(123)]

By default get_obj_type() returns obj.__class__.__name__, so you can just reuse that
to save some typing:

.. code:: python

class MyUberSchema(OneOfSchema):
type_schemas = {
'Foo': FooSchema,
'Bar': BarSchema,
}

You can customize type field with `type_field` class property:

.. code:: python

class MyUberSchema(OneOfSchema):
type_field = 'object_type
type_schemas = {
'Foo': FooSchema,
'Bar': BarSchema,
}

MyUberSchema().dump([Foo(foo='hello'), Bar(bar=123)], many=True).data
# => [{'object_type': 'Foo', 'foo': 'hello'}, {'object_type': 'Bar', 'bar': 123}]

You can use resulting schema everywhere marshmallow.Schema can be used, e.g.

.. code:: python
import marshmallow as m
import marshmallow.fields as f

class MyOtherSchema(m.Schema):
items = f.List(f.Nested(MyUberSchema))
Release History

Release History

This version
History Node

1.0

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