Iteration over a directory

ROOT
1

Dear all,

I am trying to iterate over all histograms in a directory with:

TFile* f1 = new TFile("file.root"); TList* tdf_obs = f1->GetDirectory("path/to/directory")->GetList(); TIterator* obs_it = tdf_obs->MakeIterator(); TIter iter(obs_it); std::for_each( iter.Begin(), iter.End(), fn );

where

void fn(TObject* histobj) { std::cout << histobj->GetName() << std::endl; TH2D* hist = (TH2D*)histobj->Clone(); std::cout << "information" << std::endl; }

However the list that I make on the second line is empty even though I know that there are TH2Ds in the folder. E.g. the result of ls:

TDirectoryFile* Folder Folder
KEY: TH2D 0_Image;1 0_Image
KEY: TH2D 1_Image;1 1_Image
…

Does anybody know what could be causing this?

Cheers,
Sean

2

Hi,

GetList only return the list of already loaded (and attached) objects in the directory.
You actually want to iterate over the list of keys:TFile* f1 = new TFile("file.root"); TList* tdf_obs = f1->GetDirectory("path/to/directory")->GetListOfKeys(); // no need to call MakeIterator explicitly. TIter iter(tdf_obs); std::for_each( iter.Begin(), iter.End(), fn );[code]and fn becomes:[code]void fn(TObject* key) { std::cout << key->GetName() << std::endl; TH2D* hist = (TH2D*)key->ReadObj(); std::cout << "information" << std::endl; }

Cheers,
Philippe.