This I don't like.  Either _all_ the getObjectInstances should use QVector or QList.  Unfortunately you can't overload C++ methods based on the function type.

Three options:
1. If it is too many lines of code to change all the getObjectInstances, instead take the ones that you did change and in their local code add the toList() call.
2. Change all instances of getObjectInstance to use QVector
3. add getObjectInstancesVector (ugly, I would avoid this).