About TChain

[NgJunKai]

TChain does not have Close() method (so how do we handle this guy at the end of a macro ?).
What makes it different from TFile ? any technical explaination for that ?

[jonas]

As you can see in this example tutorial, no manual deletion/closing is necessary when using TChain:
https://root.cern.ch/doc/master/df101__h1Analysis_8C.html

The resources are managed and closed automatically in the destructor of the TChain, where the files are closed as well. By the way, the TFile does the same, so if you’re correctly managing the TFile object lifetime, then you don’t even need to call Close(). In other words, if you are not memory-leaking the TFile object, then Close() is called in the constructor. Wrapping the pointer returned by TFile::Open() in a smart pointer is a good way to achieve this, like in this RNTuple tutorial:
https://root.cern.ch/doc/master/ntpl003__lhcbOpenData_8C.html

So no, there is no technical reason for that, more a historical one I guess. The TChain class is newer than TFile, and probably it was written in a time where people already understood that proper lifetime management plus deleting resources in the constructor was the way to go.