How do I track session changes with events?

[collinsmarra]

How do I track session changes with events?

[miguelgrinberg]

Ah, right! db.Session is a method that returns an instance of db.session_class, so yeah, what you did is what I intended to suggest.

[collinsmarra]

How do I track session changes with events?

I am trying to use elastic search for my app. So I was reading the micro-blog tutorial and it use flask-sqlalchemy. So events are implemented this way:

I was trying to do the same with alchemical but I cannot use sqlalchemy.events because that would result in RuntimeError: Working outside of application context.

[miguelgrinberg]

I'm not sure what is the usage that gives you working outside of app context, but Alchemical does not try to override SQLAlchemy as much as Flask-SQLAlchemy does. Setting events is done directly through SQLAlchemy, as documented here: https://docs.sqlalchemy.org/en/14/core/event.html#event-registration.

[collinsmarra]

I think that would be the line that causes the error

[miguelgrinberg]

You are using db.session outside of a request. The session does not exist then. I doubt that would even work with Flask-SQLAlchemy, you can't use the session in the global scope. For Alchemical, I think you should be able to pass the session class here, db.Session (uppercase S).

Note: it does actually work with Flask-SQLAlchemy.

[collinsmarra]

Thanks. db.Session (uppercase) would result in an error No such event 'before_commit' for target.
However db.session_class works. I am yet to investigate and learn. Thanks again