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|
:mod:`aptdaemon.client` --- The client module
=============================================
Introduction
------------
Aptdaemon comes with a client module which provides a smoother interface on top
of the D-Bus interface. It provides GObjects of the daemon and each transaction.
.. _life_cycle:
Life cycle of a transaction based action
----------------------------------------
At first you initialize an AptClient instance.
>>> from aptdaemon import client
>>>
>>> apt_client = client.AptClient()
Secondly you call the whished action, e.g. updating the package cache. It will
give you a new transaction instance.
>>> transaction = apt_client.update()
The transaction has not been started yet. So you can make some further
adjustements to it, e.g. setting a different language:
>>> transaction.set_locale("de_DE")
... or setup the monitoring of the transaction:
>>> transaction.connect("finished", on_transaction_finished)
You can then put the transaction on the queue by calling its :meth:`run()`
method:
>>> transaction.run()
If you don't need the underlying transcation instance of an action, you can
alternatively set the wait argument to True. The AptClient method will return
after the transaction is done:
>>> apt_client.update_cache(wait=True)
This can also be used with asynchronous programming, see below.
Asynchronous programming
------------------------
In the above examples simple synchronous calls have been made to the D-Bus.
Until these calls return your whole application is blocked/frozen.
In the case of password prompts this can be quite long. So aptdaemon supports
the following asynchronous styles:
D-Bus style callbacks
^^^^^^^^^^^^^^^^^^^^^
Since the client module is basically a wrapper around D-Bus calls, it provides
a pair of reply_handler and error_handler for each method. You are perhaps
already familiar with those if you have written a Python D-Bus client before:
>>> def run(trans):
... trans.run(reply_handler=trans_has_started, error_handler=on_error)
...
>>> def trans_has_started():
... pass
...
>>> def on_error(error):
... raise error
...
>>> client = AptClient()
>>> client.update(reply_handler=run, error_handler=on_error)
Deferred callbacks
^^^^^^^^^^^^^^^^^^
Aptdaemon uses a simplified version of Twisted deferreds internally, called
python-defer. But you can also make use of them in your application.
The inline_callbacks decorator of python-defer allows to write asynchronous
code in a synchronous way:
>>> @defer.inline_callbacks
... def update_cache():
... apt_client = client.AptClient()
... try:
... transaction = yield apt_client.update()
... except errors.NotAuthorizedError:
... print "You are not allowed to update the cache!"
... return
... yield transaction.set_locale("de_DE")
... yield transaction.run()
... print "Transaction has started"
.. _chaining:
Chaining Transactions
---------------------
It is possible to chain transactions. This allows to add a simple
dependency relation, e.g. you want to add a new repository, update
the cache and finally install a new package.
>>> client = aptdaemon.client.AptClient()
>>> trans1 = client.add_repository("deb", [...])
>>> trans2 = client.update_cache()
>>> trans3 = client.install_packages(["new-package"])
>>> trans2.run_after(trans1)
>>> trans3.run_after(trans2)
>>> trans1.run()
If a transaction in a chain fails all other ones which follow will
fail too with the :data:`enums.EXIT_PREVIOUS_FAILED` exit state.
Class Reference
---------------
.. autoclass:: aptdaemon.client.AptClient
:members:
.. autoclass:: aptdaemon.client.AptTransaction
:members:
Function Reference
------------------
.. autofunction:: aptdaemon.client.get_transaction
.. autofunction:: aptdaemon.client.get_aptdaemon
|
