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Command Signals
===============
:synopsis: Signals fired before and after a command is executed.
A signal is thrown pre/post each management command allowing your application
to hook into each commands execution.
Basic Example
-------------
An example hooking into show_template_tags:
::
from django_extensions.management.signals import pre_command, post_command
from django_extensions.management.commands.show_template_tags import Command
def pre_receiver(sender, args, kwargs):
# I'm executed prior to the management command
def post_receiver(sender, args, kwargs, outcome):
# I'm executed after the management command
pre_command.connect(pre_receiver, Command)
post_command.connect(post_receiver, Command)
Custom Permissions For All Models
---------------------------------
You can use the post signal to hook into the ``update_permissions`` command so that
you can add your own permissions to each model.
For instance, lets say you want to add ``list`` and ``view`` permissions to
each model. You could do this by adding them to the ``permissions`` tuple inside
your models ``Meta`` class but this gets pretty tedious.
An easier solution is to hook into the ``update_permissions`` call, as follows;
::
from django.db.models.signals import post_syncdb
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import Permission
from django_extensions.management.signals import post_command
from django_extensions.management.commands.update_permissions import Command as UpdatePermissionsCommand
def add_permissions(sender, **kwargs):
"""
Add view and list permissions to all content types.
"""
# for each of our content types
for content_type in ContentType.objects.all():
for action in ['view', 'list']:
# build our permission slug
codename = "%s_%s" % (action, content_type.model)
try:
Permission.objects.get(content_type=content_type, codename=codename)
# Already exists, ignore
except Permission.DoesNotExist:
# Doesn't exist, add it
Permission.objects.create(content_type=content_type,
codename=codename,
name="Can %s %s" % (action, content_type.name))
print "Added %s permission for %s" % (action, content_type.name)
post_command.connect(add_permissions, UpdatePermissionsCommand)
Each time ``update_permissions`` is called ``add_permissions`` will be called which
ensures there are view and list permissions to all content types.
Using pre/post signals on your own commands
-------------------------------------------
The signals are implemented using a decorator on the handle method of a management command,
thus using this functionality in your own application is trivial:
::
from django_extensions.management.utils import signalcommand
class Command(BaseCommand):
@signalcommand
def handle(self, *args, **kwargs):
...
...
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