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Grok messaging machinery

Project description


This package provides integration of z3c.flashmessage for a grok setup. This means taking care of:

  • Registering a global message receiver with the component architechture.
  • Registering by default a global session-based message source named session.
  • Optionally (if including ram.zcml) registering a global RAM stored message source named ram.
  • Providing components to make use of global message receivers and sources.

For details about what kind of messages we are talking about here, please see the z3c.flashmessage documentation.

Setting up grokcore.message

When being grokked, grokcore.message registers

  • a global session message source named session
  • a global message receiver.

Grokking of this package happens when the local configure.zcml is executed. In standard Grok-based packages this often happens automatically.

One can, of course, also grok the package manually:

>>> import grokcore.component as grok
>>> grok.testing.grok('grokcore.message')

This setups a global message receiver:

>>> from z3c.flashmessage.interfaces import IMessageReceiver
>>> from zope.component import getUtility
>>> getUtility(IMessageReceiver)
<z3c.flashmessage.receiver.GlobalMessageReceiver object at 0x...>

It also setups a session-based message source named session:

>>> from z3c.flashmessage.interfaces import IMessageSource
>>> getUtility(IMessageSource, name=u'session')
<z3c.flashmessage.sources.SessionMessageSource object at 0x...>

We provide also a RAM-stored message source that can be enabled by including ram.zcml and is not registered by default:

>>> getUtility(IMessageSource, name=u'ram')
Traceback (most recent call last):
zope.interface.interfaces.ComponentLookupError: (<InterfaceClass z3c.flashmessage.interfaces.IMessageSource>, 'ram')

You can enable this source by including ram.zcml from grokcore.message in your ZCML setup like this:

<configure xmlns="">
  <include package="grokcore.message" file="ram.zcml" />

or, of course, by registering a RAMMessageSource manually:

>>> from zope.component import provideUtility
>>> from z3c.flashmessage.sources import RAMMessageSource
>>> ram_source = RAMMessageSource()
>>> provideUtility(ram_source, name=u'ram')

Now we can get the RAM source:

>>> getUtility(IMessageSource, name=u'ram')
<z3c.flashmessage.sources.RAMMessageSource object at 0x...>

Components (API)

grokcore.message provides some extra-components and functions beside the usual components from z3c.flashmessage.


A UniqueMessageSource is a message source that holds exactly zero or one message. Note that messages are not stored persistent in a UniqueMessageSource instance and will be lost after restarting your Zope instance.

It is a baseclass, which means that you have to derive from it to register an instance as global utility upon your software being grokked (see examples below).


UniqueMessageSource.send(message[, type=u’message’])
Send a message message of type type.
Returns a generator object listing the message if one is stored.
Delete the message stored from source, if message is this message.

Convenience functions

grokcore.message provides a couple of convenience functions to feed sources or get data from them.

grokcore.message.send(message[, type=’message’[, name=’session’]])

Send message to the message source name.

Returns True if the message could be sent successfully. Otherwise False is returned:

>>> import grokcore.message
>>> grokcore.message.send('Meet at dawn!')
>>> grokcore.message.send('Meat a fawn!', name='doesnotexist')


Get a list of messages stored at message source registered under name name or None.

This action never deletes messages from the queried source.

>>> import grokcore.message
>>> grokcore.message.get_from_source('session')
<generator object ...>
>>> grokcore.message.get_from_source('not-existing') is None


Receive the messages collected by the receiver registered under name name.

>>> import grokcore.message
>>> msgs = list(grokcore.message.receive())
>>> msgs
[<z3c.flashmessage.message.Message object at 0x...>]
>>> msgs[0].message
'Meet at dawn!'

Please note, that this action might delete messages from the sources they have been sent to as by ‘receiving’ messages you indicate that the messages have been processed.

The session source for instance is now empty:

>>> list(grokcore.message.get_from_source('session'))

Receiving again will give no results:

>>> list(grokcore.message.receive())


Creating a UniqueMessageSource:

>>> from grokcore.message import UniqueMessageSource
>>> class MyUniqueMessageSource(UniqueMessageSource):

After being grokked, the source is automatically registered:

>>> grok.testing.grok_component(
...     'MyUniqueMessageSource', MyUniqueMessageSource,
...     dotted_name='grokcore.message.tests')
>>> source = getUtility(IMessageSource, name='uniq_source')
>>> source
<...MyUniqueMessageSource object at 0x...>

It provides the methods required by the IMessageSource interface:

>>> from z3c.flashmessage.interfaces import IMessageSource
>>> from zope.interface import verify
>>> verify.verifyClass(IMessageSource, MyUniqueMessageSource)

We can list the message stored in the source:

>>> source.list()
<generator object ...>
>>> list(source.list())
>>> source.send(message='Hello!', type='message')
>>> list(source.list())
[<z3c.flashmessage.message.PersistentMessage object at 0x...>]
>>> print(list(source.list())[0].message)

When we send another message, the old one will be silenty discarded:

>>> source.send(message='Hello again!', type='message')
>>> len(list(source.list()))
>>> print(list(source.list())[0].message)
Hello again!

We can delete the message:

>>> msg = list(source.list())[0]
>>> source.delete(msg)
>>> len(list(source.list()))

Examples for the convenience functions can be found above.


3.0.1 (2018-01-17)

  • Replace the use of grok.implements() with the @grok.implementer() directive throughout.

3.0.0 (2018-01-15)

  • Python 3 compatibility.

0.4.3 (2016-02-15)

  • Update tests.

0.4.2 (2010-10-25)

  • Tests fixed by explicitely registering the IClientIdManager and ISessionDataContainer utilities. The ftesting.zcml was re-introduced for this.

0.4.1 (2010-10-25)

  • Remove ftesting.zcml that was not necessary anymore.

0.4 (2010-10-25)

  • Make sure zope.session is configured, as this package claims to provide for a session based flash message machinery.
  • Made package comply to repository policy.

0.3 (2010-03-05)

  • UniqueMessageSource now implements the IMessageSource interface completely, i.e. the type parameter is now optional when using UniqueMessageSource.send().

0.2 (2010-03-03)

  • The utility function send now takes a name argument, allowing the choice of the target message source.

0.1 (2010-03-03)

  • Factored out from former versions of grokui.admin, grok and megrok.layout respectively.

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