Hi Mark,
When you do something like:
TFile f("afile.root","recreate");
TTree *T = new TTree("T","example");
T->Branch(...
T is automatically associated to the current directory (here f).
When filling the Tree, you do not have to cd to the corresponding
directory. This will be automatically done by TTree::Fill
and the actual current directory restored.
For more details, see the chapter about Object Ownership in
the Users Guide.
Rene Brun
On Thu,
12
Jun 2003
mark.winkler@philips.com
wrote:
> Hello Rooters,
>
> Could someone spell out the relationship between TFile and TTree classes?
> My motivation in asking is a desire to read from an existing tree, process
> some data, write results to a separate (previously non-existent) tree, and
> then go back to reading from tree 1 in order to repeat -- thus several
> trees would be open at the same time -- all of which "belong" to different
> files.
>
> I am a little unclear how a tree gets "linked" to a given file. Reading
> seems fairly intuitive: open a file, then "Get" part of that file with
> the name of the tree. However, writing seems like a bit of a mystery to
> me: declare a file, and then the first tree declared after it is "its"
> tree?
>
> I know the forum desires specific problems with code/etc.-- my apologies
> in advance to any offended!
>
> Thanks!
> Mark
>
>
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