Question

In my app i need to save changed values (old and new) when model gets saved. Any examples or working code?

I need this for premoderation of content. For example, if user changes something in model, then administrator can see all changes in separate table and then decide to apply them or not.

Answer 1

You haven’t said very much about your specific use case or needs. In particular, it would be helpful to know what you need to do with the change information (how long do you need to store it?). If you only need to store it for transient purposes, @S.Lott’s session solution may be best. If you want a full audit trail of all changes to your objects stored in the DB, try this AuditTrail solution.

UPDATE: The AuditTrail code I linked to above is the closest I’ve seen to a full solution that would work for your case, though it has some limitations (doesn’t work at all for ManyToMany fields). It will store all previous versions of your objects in the DB, so the admin could roll back to any previous version. You’d have to work with it a bit if you want the change to not take effect until approved.

You could also build a custom solution based on something like @Armin Ronacher’s DiffingMixin. You’d store the diff dictionary (maybe pickled?) in a table for the admin to review later and apply if desired (you’d need to write the code to take the diff dictionary and apply it to an instance).