Run action when I delete an xblock from studio

[Juan Carlos Hierro]

Good,

I am developing an xblock and I need to execute an action (hook) when I delete this xblock from the studio. If possible I would like a solution without having to modify the core.

Thanks and regards!

[David Ormsbee]

Hi Juan,

There's a Django signal emitted whenever an item is deleted from a course. You should be able to listen for that with your own code without touching anything in core. You can see an example of listening for it here:

https://github.com/edx/edx-platform/blob/dda92d13198b935f8ebaaaf1ab29b3f05c2ec6ea/cms/djangoapps/contentstore/signals.py#L63-L75

Keep in mind that catching the signal happens synchronously in the same transaction as the request to delete the item. If you're going to do anything that might fail or take a long time (like a POST over a network connection), you'll probably want to make "my_handler" spin off a celery task instead so that it can run in the background and not slow down the act of deletion. It might look something like this:

from django.dispatch import receiver

from xmodule.modulestore.django import SignalHandler

from lms import CELERY_APP

@receiver(SignalHandler.item_deleted)

def my_handler(**kwargs):

    usage_key = kwargs.get('usage_key') # This is what identifies the unit that was deleted

    user_id = kwargs.get('user_id')     # This is the user who did the deleting

    course_key = usage_key.course_key   # The identifier for the course it was deleted from.

    do_something_slow.apply_async(args=(usage_key,))

@CELERY_APP.task(name='mymodule.tasks.do_something_slow')

def do_something_slow(usage_key):

    # Whatever slow operation you need to do.

    # If you need to make a network request, please use the "requests" library and

    # be sure to use timeouts.

I'm a little fuzzy on that celery syntax, but I think that's it. Hope that helps.

Take care.

Dave

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[Juan Carlos Hierro]

Thanks for your help. But before I update the open edx version because the "SignalHandler" class does not have the "item_deleted" attribute.