Header files for Trees

[Cathy]

Dear All,

I need some general guidance, this may turn out to be more of a C++ question, but since i am using ROOT i thought this would be the best place to start. I have a large analysis that i am trying to make more modular. My issue now is that i have probalby about 100 branches in a TTree that i have to
declare at the top of my root macro. so basically i have

void analysis()
{
..
tree->Branch("name1", "title1")
tree->Branch("name2", "title2")
...
...
tree->Branch("name100", "title100")
}

i would love to have these hundred or so lines removed from my code and put into a header file.
i tried this by simply moving these definitions into a file “tree.h” with the proper header file syntax, and got a message:

error: expected constructor, destructor, or type conversion before ‘->’ token

I read somewhere that this error is because this syntax requires processing and the header file
does not do this. So, if not a header file then how would you best modularize a code so you dont
have 100’s of lines of branch declarations?

Any suggestions for how to achieve this?

Many Thanks,
Cathy

[Wile_E_Coyote]

“Most recent” documentation about how to generate and use an “analysis skeleton”:

• TTree::MakeClass (see also “ROOT User’s Guide” → “Trees” → “Using TTree::MakeClass”)

• TTree::MakeSelector (see also “ROOT Primer” → “File I/O and Parallel Analysis” → “N-tuples in ROOT” → “For the advanced user: Processing trees with a selector script” and “ROOT User’s Guide” → “Trees” → “Using TTree::MakeSelector” and “ROOT User’s Guide” → “Example Analysis”)

• TTree::MakeProxy

• ROOT::RDataFrame (uses the TTreeReader class internally) and the Data Frame tutorials (when using ROOT 6.14 or newer)

Notes:

• if you work with a TChain, you should generate the “analysis skeleton” for the whole TChain, not for a single TTree

• if you plan to use TTree:CloneTree, see this post and that post and this thread
  and grep -r CloneTree ${ROOTSYS}/t[eu]*

• for the TTreeReader class (not available in ROOT 5), see the ${ROOTSYS}/tutorials/tree/*Reader* files and the result of TTree:MakeSelector when run with ROOT 6.06 or newer (note: use the "=legacy" option, if you want to generate a pre-ROOT-6 selector)

• you may also be interested in: TFile::MakeProject