Reading alias of branches in a loop?

[Demosthene]

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ROOT Version: 6.18/04
Platform: Centos7
Compiler: gcc 8.3.0

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I have two different types of ROOT files, according to the data they contain - let’s call them A and B. Specifically, they both contain a TTree with the same name and the same branches, except for one special branch called var_A or var_B depending on the input file.

I am currently retrieving this branch in a way that is consistent for any input as:

type var_global;
...
tree->SetBranchStatus("var_*",1);
TBranch* brA = (TBranch*)tree->GetListOfBranches()->FindObject("var_A");
TBranch* brB = (TBranch*)tree->GetListOfBranches()->FindObject("var_B");
if (brA)      tree->SetBranchAddress("var_A",&var_global);
else if (brB) tree->SetBranchAddress("var_B",&var_global);

What if var_A in file A is no longer one branch, but two branches var_A1 and var_A2? With TTree::Draw I can set up an alias

if (brA) tree->SetAlias("var_global", "(var_A1||var_A2)");

Is there a way to do something similar to an alias when looping over the tree and retrieving these branches with TTree::GetEntry?

[couet]

I guess @pcanal can help you.

[pcanal]

Is there a way to do something similar to an alias when looping over the tree and retrieving these branches with TTree::GetEntry ?

No unless you are using directly a TTreeFormula (the gut of the TTree::Draw). You may want to investigate using RDataFrame.