https://community.graphisoft.com/t5/Archicad-C-API/How-to-react-to-AddOnObject-changes/m-p/706457#M10948 <P>If I understand it correctly, the benefit of&nbsp;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?</P><P>&nbsp;</P><P>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.&nbsp;ACAPI_Element_AttachObserver does not work, AddOnObjects are no real objects despite being addressed via GUID.</P><P>&nbsp;</P><P><FONT face="courier new,courier" color="grey">Operating system used: <EM>Windows </EM></FONT></P> Thu, 25 Jun 2026 07:54:30 GMT SimonWeinberger 2026-06-25T07:54:30Z https://community.graphisoft.com/t5/Archicad-C-API/How-to-react-to-AddOnObject-changes/m-p/706457#M10948 <P>If I understand it correctly, the benefit of&nbsp;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?</P><P>&nbsp;</P><P>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.&nbsp;ACAPI_Element_AttachObserver does not work, AddOnObjects are no real objects despite being addressed via GUID.</P><P>&nbsp;</P><P><FONT face="courier new,courier" color="grey">Operating system used: <EM>Windows </EM></FONT></P> Thu, 25 Jun 2026 07:54:30 GMT https://community.graphisoft.com/t5/Archicad-C-API/How-to-react-to-AddOnObject-changes/m-p/706457#M10948 SimonWeinberger 2026-06-25T07:54:30Z