Thanks for the reply.
>
> Are you sure that instead of:
>
> int* evptr = 0;
> amstree->SetBranchAddress("Eventno",&evptr)
>
> you should may be have :
>
>
> EventNtuple02* event = 0;
> amstree->SetBranchAddress("event02",&event);
>
> For sure int* must be wrong.
>
Yes, the latter works. But in the former, I am trying to access a
sub-branch directly. (I'm actually working with some code that
supposedly used to work, and which contains a construction similar to
the former).
The tree has split branches.
The Root web page says about the split option:
"If you run the program above and set split = 1, then the statement:
tree->Branch("event", "Event", &event, bsize,split);
will generate several branches, one for each data member of the Event class."
I've been assuming that this means that each data member of the
EventNtuple02 class, e.g. Eventno, becomes a branch unto itself, and
behaves like any other branch (and so should have its address set with a
pointer of its respective data member type). Indeed, TTree::GetBranch
seems to find the sub-branch successfully.
I have tried also things like
amstree->SetBranchAddress("Eventno", &(event02->Eventno));
but still no luck-- nothing gets read by GetEvent for this case.
Probably I'm misunderstanding what the difference is between split
tree branches and regular branches is. What am I missing?
Kate.
> Rene Brun
>
> Kate Scholberg wrote:
> >
> > Hi,
> >
> > I have a root file containing trees generated with
> > split branches,
> >
> > For instance:
> >
> > EventNtuple02 _event02;
> > static void *pev2=(void*)&_event02;
> > TBranch *b2=_tree->Branch("event02", "EventNtuple02", &pev2, 64000,1);
> >
> > The EventNtuple02 class is a simple one, containing basic data types
> >
> > class EventNtuple02: public TObject {
> > public:
> > int Eventno;
> > int Run;
> > ...
> > };
> >
> > When I try to read the file in a standard way, as follows:
> >
> > {
> >
> > // Load shared lib etc..
> >
> > TFile file("prv3.root","UPDATE");
> > TTree *amstree = (TTree*)file->Get("AMSRoot");
> > EventNtuple02* event02 = new EventNtuple02;
> > amstree->SetBranchAddress("event02",&event02);
> >
> > int nevent = amstree.GetEntries();
> >
> > for(int i=0;i<nevent;i++)
> > {
> >
> > amstree->GetEvent(i);
> > printf("Run, event %d %d\n",event02->Run, event02->Event);
> >
> > }
> >
> > }
> >
> > No problem... all fine.
> >
> > But what I would like to do is access directly one of the sub-branches
> > of the event02 branch.
> >
> > int* evptr = 0;
> > amstree->SetBranchAddress("Eventno",&evptr)
> >
> > This seems to find the sub-branch correctly.
> > Also if I get the sub-branch with
> > TBranch *evbranch = amstree->GetBranch("Eventno");
> > it Prints OK.
> >
> > However, then
> >
> > amstree.GetEvent(i)
> >
> > doesn't seem to read anything into evptr.
> >
> > (and doing explicitly evbranch->GetEntry(i,1) returns nbytes=1).
> >
> > Is this the expected behavior for sub-branches?
> >
> > I haven't looked into the source, but from my not-extremely-thorough
> > reading of the docs I would expect SetAddress to create an int, have
> > evptr point to it, and GetEvent would put stuff into it from the
> > branch.
> >
> > Same behavior if the int evptr points to is already instantiated,
> > i.e. int* evptr= new int;
> >
> > Same behavior on Linux and OSF1, with Root versions 2.22, 2.25 and 3.00
> >
> > Kate Scholberg
> > schol@mit.edu
>
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