Drawing objects in a file

From: Stephan Zimmer <zimmerst_at_googlemail.com>
Date: Thu, 28 Apr 2011 00:37:18 +0200

Hi Rooters,
suppose I have a file that contains a number of objects (which I cannot really influence):
root [1] .ls

TFile**		temp.root	
 TFile*		temp.root	
  OBJ: TH2F	hist0	 : 0 at: 0xaa08418
  KEY: TH2F	hist0;1	
  KEY: TGraphErrors	Graph;44	Graph
  KEY: TGraphErrors	Graph;43	Graph
  KEY: TGraphErrors	Graph;42	Graph
  KEY: TGraphErrors	Graph;41	Graph
  KEY: TGraphErrors	Graph;40	Graph
  KEY: TGraphErrors	Graph;39	Graph
  KEY: TGraphErrors	Graph;38	Graph
  KEY: TGraphErrors	Graph;37	Graph
  KEY: TGraphErrors	Graph;36	Graph
  KEY: TGraphErrors	Graph;35	Graph
  KEY: TGraphErrors	Graph;34	Graph
  KEY: TGraphErrors	Graph;33	Graph
  KEY: TGraphErrors	Graph;32	Graph
  KEY: TGraphErrors	Graph;31	Graph
  KEY: TGraphErrors	Graph;30	Graph
  KEY: TGraphErrors	Graph;29	Graph
  KEY: TGraphErrors	Graph;28	Graph
  KEY: TGraphErrors	Graph;27	Graph
  KEY: TGraphErrors	Graph;26	Graph
  KEY: TGraphErrors	Graph;25	Graph
  KEY: TGraphErrors	Graph;24	Graph
  KEY: TGraphErrors	Graph;23	Graph
  KEY: TGraphErrors	Graph;22	Graph
  KEY: TGraphErrors	Graph;21	Graph
  KEY: TGraphErrors	Graph;20	Graph
  KEY: TGraphErrors	Graph;19	Graph
  KEY: TGraphErrors	Graph;18	Graph
  KEY: TGraphErrors	Graph;17	Graph
  KEY: TGraphErrors	Graph;16	Graph
  KEY: TGraphErrors	Graph;15	Graph
  KEY: TGraphErrors	Graph;14	Graph
  KEY: TGraphErrors	Graph;13	Graph
  KEY: TGraphErrors	Graph;12	Graph
  KEY: TGraphErrors	Graph;11	Graph
  KEY: TGraphErrors	Graph;10	Graph
  KEY: TGraphErrors	Graph;9	Graph
  KEY: TGraphErrors	Graph;8	Graph
  KEY: TGraphErrors	Graph;7	Graph
  KEY: TGraphErrors	Graph;6	Graph
  KEY: TGraphErrors	Graph;5	Graph
  KEY: TGraphErrors	Graph;4	Graph
  KEY: TGraphErrors	Graph;3	Graph
  KEY: TGraphErrors	Graph;2	Graph
  KEY: TGraphErrors	Graph;1	Graph

root [2]

I'm wondering why the following method of accessing the elements in a file does not work:

  TFile *f = new TFile("temp.root","r");   TIter nextkey(f->GetListOfKeys());
  TKey *key;
  while (key = (TKey*)nextkey()) {
    TObject *obj = (TObject*)key->ReadObj();     obj->Draw();
  }

it doesn't complain but it doesn't show anything either. On the other hand, if i open the same file with the TBrowser it draws without complaints. As for the reference, I'm using Root 5.27/06 Could someone be so kind and help me figuring out what's going on here?

Cheers and thanks,
Stephan

-- 
Stephan Zimmer
zimmerst_at_gmail.com

Received on Thu Apr 28 2011 - 00:37:30 CEST