Passing histograms between functions

[Vangi]

Dear rooters,
I guess my question is not connected to ROOT or to histograms specifically, but…
I am trying to generate a few histograms, then loop over my events, fill the histograms in, then, outside the loop, save them in a file. This works fine, but now, I want to place my histogram initialisation in a function in another file, the filling of the histograms in a second, and the saving in a third, so my main macro looks like this:

#include "InitHistos.h"
#include "FillHistos.h"
#include "SaveHistos.h"
void func(){

   initialiseHistos();
   for(int i{0};i<ev_number;++i){
   .....
      fillHistos(....);
   }
   saveHistos();
}

I am not sure how to make fillHistos “see” the histograms that I have without initialising them as global variables.
Thank you,
Vangi

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ROOT Version: Not Provided
Platform: Not Provided
Compiler: Not Provided

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[Danilo]

Hi,

the way to percolate the information through the functions is to pass it as parameter. In your case this could be a reference to the collection of your histograms, e.g.:

void DoSomethingWithHistos(std::forward_list<std::unique_ptr<TH1F>> &histos);

Cheers,
D

[Vangi]

Hello,
Thank you for your answer,
Vangi