If you want this functionality, you cannot use the split mode, unless
your objects mFoo and mBar are part of the same branch.
Note that if you need links between branches, this means that you need
the two branches in memory. There is no need to split in this case.
There is a technical difficulty in supporting this facility. You can
read only one branch, and in case you read the two branches, this may
happen
in the order (branch1, branch2) or (branch2,branch1).
In case of pointers to TClonesArray, I have announced several times our
intention to support references to objects in a TClonesArray.
Rene Brun