Problems with changing the name of collectable string class in a root file

[bengy]

Hello everyone,
I get a problem in changing the name of collectabe string class in a root file. My root file, which is called ZJetsToNuNu_HT1200To2500_ext1.root, has the following structure:

I would like to change the name of the the first item named “tag” into “untagged”. When I point to it is says that item is a collectable string class. How can I change the name of it and save into a new root file?

I have tried like,

TFile *f = new TFile("ZJetsToNuNu_HT1200To2500_ext1.root", "update");
TObjString *tag;
f->GetObject("tag", tag)
tag->SetString("untagged");
f->Write();

However, it does not change anything.

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ROOT Version (5.34/36):

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Best wishes,
Bengy

[etejedor]

Hi @bengy,

Can you try adding tag->Write() before f->Write() ?

Cheers,

Enric

[bengy]

Hi @etejedor,
It creates a new TObjString with “untagged” now, but the original “tag” is still there.
Best,
Bengy

[etejedor]

Hi @bengy,

Can you try to delete the old “tag” by using TFile::Delete:

TFile::Delete a TObject from a directory

[quote]Q2. After closing and reopening the file the ls() changes and no directory is shown.[/quote] humm … f.Open("test.root", "READ");Does NOT affect the object ‘j’ because TFile::Open is a static function that allocates and return a new object. i.e. TFile *f2 TFile::Open("test.root", "READ"); f2->ls(); f2->Close();will work better. Cheers, Philippe.

Please also check the method documentation here:

https://root.cern.ch/doc/v612/classTFile.html#a1b1c78f1d20439291bb52f2217c382f7

Cheers,

Enric