How do i store a TLegend in a ROOT-Directory?

ROOT
1

Hi all.
How can I store (and restore) a TLegend-Object in a ROOT-Directory. To store i use the following (sorry for dirty CINT syntax :wink: )

legend = new TLegend(0.4,0.5,0.6,0.7);
legend->SetName(“myLegend”);
gDirectory->GetList()->Add(legend) ;
// compare with other objects:
multi= new TMultiGraph(“myMulti”,“myMulti”) ;
gDirectory->GetList()->Add(multi);
//
//
gDirectory->ls();
Produces the output.

TROOT* Rint The ROOT of EVERYTHING
TLegend X1= 0.400000 Y1=0.500000 X2=0.600000 Y2=0.700000 myLegend
OBJ: TMultiGraph myMulti myMulti : 0 at: 0x8978f08

Note teh missing "OBJ: " in front of TLegend.
Getting the TLegend back from the directory is not possible to me:
gDirectory->FindObject(“myLegend”)
Produces:
(const class TObject*)0x0

Please tell me how to store a TLegend properly in a directory,
Cheers,
J.

2

Hi,

If you have only one legend, you can retrieve it using:

If you have more than on TLegend, you will need to wrap them in a holder class inheriting from TNamed (so that you can actually set a name)

Cheers,
Philippe.

3

That’s what I thought, too, but at least with ROOT 3.10 this also does not work.

4

Only classes that implement the function IsSortable returning kTRUE can be added to a TDirectory (this is a THashList).

I will implement this function and the associated function Hash for all TPave family classes in the next version.

Rene

5

Thank you, for this answer. Is this fact (about TDirectory or even about THasLIst) written in the ROOT Users Guide (and I only oversaw it) or should i write this as request do the “ROOT Documentation” forum :wink: ?