123 lines
4.3 KiB
ReStructuredText
123 lines
4.3 KiB
ReStructuredText
.. _stanzabase:
|
|
|
|
==============
|
|
Stanza Objects
|
|
==============
|
|
|
|
.. module:: sleekxmpp.xmlstream.stanzabase
|
|
|
|
The :mod:`~sleekmxpp.xmlstream.stanzabase` module provides a wrapper for the
|
|
standard :mod:`~xml.etree.ElementTree` module that makes working with XML
|
|
less painful. Instead of having to manually move up and down an element
|
|
tree and insert subelements and attributes, you can interact with an object
|
|
that behaves like a normal dictionary or JSON object, which silently maps
|
|
keys to XML attributes and elements behind the scenes.
|
|
|
|
Overview
|
|
--------
|
|
|
|
The usefulness of this layer grows as the XML you have to work with
|
|
becomes nested. The base unit here, :class:`ElementBase`, can map to a
|
|
single XML element, or several depending on how advanced of a mapping
|
|
is desired from interface keys to XML structures. For example, a single
|
|
:class:`ElementBase` derived class could easily describe:
|
|
|
|
.. code-block:: xml
|
|
|
|
<message to="user@example.com" from="friend@example.com">
|
|
<body>Hi!</body>
|
|
<x:extra>
|
|
<x:item>Custom item 1</x:item>
|
|
<x:item>Custom item 2</x:item>
|
|
<x:item>Custom item 3</x:item>
|
|
</x:extra>
|
|
</message>
|
|
|
|
If that chunk of XML were put in the :class:`ElementBase` instance
|
|
``msg``, we could extract the data from the XML using::
|
|
|
|
>>> msg['extra']
|
|
['Custom item 1', 'Custom item 2', 'Custom item 3']
|
|
|
|
Provided we set up the handler for the ``'extra'`` interface to load the
|
|
``<x:item>`` element content into a list.
|
|
|
|
The key concept is that given an XML structure that will be repeatedly
|
|
used, we can define a set of :term:`interfaces` which when we read from,
|
|
write to, or delete, will automatically manipulate the underlying XML
|
|
as needed. In addition, some of these interfaces may in turn reference
|
|
child objects which expose interfaces for particularly complex child
|
|
elements of the original XML chunk.
|
|
|
|
.. seealso::
|
|
:ref:`create-stanza-interfaces`.
|
|
|
|
Because the :mod:`~sleekxmpp.xmlstream.stanzabase` module was developed
|
|
as part of an `XMPP <http://xmpp.org>`_ library, these chunks of XML are
|
|
referred to as :term:`stanzas <stanza>`, and in SleekXMPP we refer to a
|
|
subclass of :class:`ElementBase` which defines the interfaces needed for
|
|
interacting with a given :term:`stanza` a :term:`stanza object`.
|
|
|
|
To make dealing with more complicated and nested :term:`stanzas <stanza>`
|
|
or XML chunks easier, :term:`stanza objects <stanza object>` can be
|
|
composed in two ways: as iterable child objects or as plugins. Iterable
|
|
child stanzas, or :term:`substanzas`, are accessible through a special
|
|
``'substanzas'`` interface. This option is useful for stanzas which
|
|
may contain more than one of the same kind of element. When there is
|
|
only one child element, the plugin method is more useful. For plugins,
|
|
a parent stanza object delegates one of its XML child elements to the
|
|
plugin stanza object. Here is an example:
|
|
|
|
.. code-block:: xml
|
|
|
|
<iq type="result">
|
|
<query xmlns="http://jabber.org/protocol/disco#info">
|
|
<identity category="client" type="bot" name="SleekXMPP Bot" />
|
|
</query>
|
|
</iq>
|
|
|
|
We can can arrange this stanza into two objects: an outer, wrapper object for
|
|
dealing with the ``<iq />`` element and its attributes, and a plugin object to
|
|
control the ``<query />`` payload element. If we give the plugin object the
|
|
name ``'disco_info'`` (using its :attr:`ElementBase.plugin_attrib` value), then
|
|
we can access the plugin as so::
|
|
|
|
>>> iq['disco_info']
|
|
'<query xmlns="http://jabber.org/protocol/disco#info">
|
|
<identity category="client" type="bot" name="SleekXMPP Bot" />
|
|
</query>'
|
|
|
|
We can then drill down through the plugin object's interfaces as desired::
|
|
|
|
>>> iq['disco_info']['identities']
|
|
[('client', 'bot', 'SleekXMPP Bot')]
|
|
|
|
Plugins may also add new interfaces to the parent stanza object as if they
|
|
had been defined by the parent directly, and can also override the behaviour
|
|
of an interface defined by the parent.
|
|
|
|
.. seealso::
|
|
|
|
- :ref:`create-stanza-plugins`
|
|
- :ref:`create-extension-plugins`
|
|
- :ref:`override-parent-interfaces`
|
|
|
|
|
|
Registering Stanza Plugins
|
|
--------------------------
|
|
|
|
.. autofunction:: register_stanza_plugin
|
|
|
|
ElementBase
|
|
-----------
|
|
|
|
.. autoclass:: ElementBase
|
|
:members:
|
|
:private-members:
|
|
:special-members:
|
|
|
|
StanzaBase
|
|
----------
|
|
|
|
.. autoclass:: StanzaBase
|
|
:members:
|