Hi Gene,
I suspect you do not load the class definition of the StGG class.
You are splitting the object by setting the split-level (the last parameter)
to 1.
>m1->Branch("br1","StGG",&v1,64000,1);
This will create a branch for each data member of the StGG class, and allows
you to directly access any of them by typing:
>m1->Scan("val1");
To make Scan work with the class and method name you will have to load the
class definition.
> m1->Scan("br1.Val()");
For example to use the event methods on the Event.root file in the
$ROOTSYS/test directory, you have to load the libEvent.so to make the Event
class available:
>.L libEvent.so
> TFile f("$ROOTSYS/test/Event.root")
> T->Scan("event.GetTemperature()")
It looks like your allocation of an instance, causes the class to laod. Try
making an instance, and then try:
m1->Scan("br1.Val()");
>If I actually allocate an instance of the class,
>set the TTree branch address to it, and then
>call GetEvent() on the TTree, then the member
>functions work correctly on the instance of
>the class...
Cheers,
Suzanne
-----Original Message-----
From: Gene Van Buren <gene@bnl.gov>
To: roottalk@pcroot.cern.ch <roottalk@pcroot.cern.ch>
Date: Wednesday, March 08, 2000 10:28 AM
Subject: Using stored class member funcs in TTrees
>Hi - I'm wondering if there's something special
>I need to do in order to be able to use member
>functions of a class I store with a TTree in the Draw()
>or Scan() functions of the TTree???
>
>I'm using Root 2.23/12.
>
>I have tried storing a class (StGG) with just four members;
>a function Gene() wihich returns the float 3.5
>a float data member val1
>a function Val() which returns val1
>a function Add() which adds 1.0 to val1
>
>When I store a bunch of these in a TTree, save it
>to a file, and then look at the TTree in the file:
>All the values of val1 appear to be correct,
>but both Gene() and Val() return garbage.
>
>I store the class in a macro like this:
>
>{
>gSystem->Load("...");
>TFile a1("gg.root","RECREATE");
>StGG* v1 = new StGG();
>TTree* m1 = new TTree("myTree","This is my tree");
>m1->Branch("br1","StGG",&v1,64000,1);
>for (int i=0; i<25; i++) {
> v1->Add();
> m1->Fill();
>}
>a1.Write();
>a1.Close();
>}
>
>I then read it back into memory in another Root
>session:
>
>gSystem->Load("...");
>TFile a1("gg.root");
>TTree* m1 = (TTree*) a1.Get("myTree");
>
>If I type:
>m1->Scan("val1");
>everything looks like I expect. But if I type
>m1->Scan("br1.Val()");
>or
>m1->Scan("br1.Gene()");
>all 25 values come out as zero or garbage.
>Scan() doesn't even complain if I enter a
>bogus member name - spits back
>zeros or garbage also! Draw() at least
>requires that I get the member name
>correct (e.g., Draw("Val()") returns an
>error, while Draw("br1.Val()") draws a hist
>with 25 entries at zero).
>
>If I actually allocate an instance of the class,
>set the TTree branch address to it, and then
>call GetEvent() on the TTree, then the member
>functions work correctly on the instance of
>the class...
>
>...Just not in the Draw() and Scan() of the TTree.
>Anyone know why?
>
>-Gene Van Buren
>
>
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