topic Re: How to react to AddOnObject changes? in Archicad C++ API

How to react to AddOnObject changes?

SimonWeinberger — Thu, 25 Jun 2026 07:54:30 GMT

If I understand it correctly, the benefit of ACAPI_AddOnObject_* methods over ACAPI_ModulData_* is that you can a) perform changes inside an undo scope and b) sync the data to the server (and other people). But how can I react to this happening?

I'd like to know when there are changes to AddOnObjects due to undo/redo or sync with server, but I couldn't find any events handling this. What are the methods I need to use for this? e.g. ACAPI_Element_AttachObserver does not work, AddOnObjects are no real objects despite being addressed via GUID.

Operating system used: Windows

Re: How to react to AddOnObject changes?

Tamas Polyak — Fri, 26 Jun 2026 12:19:37 GMT

Hi,

Please check here: Archicad 29 C++ API: Add-On Objects

It states the requirements for the notifications to work. Please report it if it still doesn't work.

Best regards,

Tamás

Re: How to react to AddOnObject changes?

SimonWeinberger — Fri, 26 Jun 2026 14:40:30 GMT

The methods you mentioned do work, but they don't cover the scenario I'm interested in. The user performing undo/redo does not call the installed handlers, only load/save of an older archicad file format does so.