[TYPO3-english] Action when changing relations in backend

[Christian Zenker]

Hi.

I am looking for a possibility to call some method if a user changes  
related items of a model.
The Datamap-Hooks are usually fine for this, but I could not find any way  
to detect if items where added or removed from a group field to an other  
table. Has any one done this and could point me to an example or has any  
other hint?

Background is the calendar extension based on extbase[1]. All events are  
getting indexed to increase performance for recurring events. But the  
indexing should only be done if it is actually needed. So if you just  
change the title of an event, indexing is not necessary and should not be  
done. That's why I check if any "critical" field was changed at all before  
reindexing in the "processDatamap_afterDatabaseOperations"-Hook. But I  
could not find a clean solution on how to detect if a relation to the  
exceptions table was updated. The relation is done via the group type and  
a MM-relation between those tables.

I would be grateful for any hints.

Christian.

[1] http://forge.typo3.org/projects/extension-cz_simple_cal