Hi Ed,
You can see if a class is persistable by looking in the include file
for the ClassDef statement. If the ClassDef is missing or the class version
number is 0, this class cannot be made persistent. This was the case
for TExMap before my change.
There are many ways to solve your problem (Tree being one).
You can see how TExMap::Streamer is now implemented at:
http://root.cern.ch/root/htmldoc/src/TExMap.cxx.html#TExMap:Streamer
Rene Brun
Edward Moyse wrote:
>
> Hi Rene,
>
> Thanks! Is there any other way to achieve the same effect in current code? I
> guess I could iterate through TExMap and put value and keys into a normal
> TTree, then read them back in again. Is there an easier way to do it?
>
> The problem is that whilst I can check out and compile the CVS code, the
> analysis I'm writing needs to be used by lots of other people.
>
> Cheers,
>
> Ed
>
> P.S. If there are other classes that are not designed to be persistent, could
> you print an error message if the Write() method is used? It's pretty
> confusing that TExMap has a method which does nothing, but returns no error
>
> On Monday 23 June 2003 9:13 am, you wrote:
> > Hi Ed,
> >
> > TExMap was not designed to be persistent.
> > I have modified the class such that your example works.
> > Now in CVS.
> >
> > Rene Brun
> >
> > Edward Moyse wrote:
> > > > The problem is you didn't write your TExMap in the file, so it's normal
> > > > you can't get it back afterwards ;-)
> > >
> > > Oops! ;-)
> > >
> > > > However if you replace
> > > >
> > > > hfile->Write("TestMap", TObject::kSingleKey);
> > > >
> > > > with
> > > >
> > > > testMap->Write();
> > >
> > > That was a typo. I actually meant to do:
> > > testMap->Write("TestMap", TObject::kSingleKey);
> > > because I had already tried the approach you suggested, and got/get the
> > > following problem:
> > >
> > > root [0] TFile* hfile = new TFile("test.root","RECREATE");
> > > root [1] TExMap* testMap = new TExMap();
> > > root [2] testMap->Add(1,2);
> > > root [3] testMap->Add(2,56);
> > > root [4] testMap->Add(3,256);
> > > root [5] cout << (testMap->GetValue(2))<<endl;;
> > > 56
> > > root [6] cout << (testMap->GetValue(1))<<endl;;
> > > 2
> > > root [8] testMap->Write();
> > > root [9] hfile->Close();
> > > root [10] gROOT->Reset()
> > >
> > > Sure enough the TExMap appears to be added to the root file properly:
> > >
> > > root [14] TFile f("test.root")
> > > root [15] f.ls()
> > > TFile** test.root
> > > TFile* test.root
> > > KEY: TExMap TestMap;1 Map with external hash
> > >
> > > But I can't seem to "Get" it properly:
> > >
> > > root [12] TExMap *map = (TExMap*)f2.Get("TExMap");
> > > root [13] cout << (map->GetValue(2))<<endl;;
> > > 0
> > > root [14] cout << (map->GetValue(1))<<endl;;
> > > 0
> > >
> > > i.e. it seems to be empty!
> > >
> > > Any help would be much appreciated!
> > >
> > > Cheers,
> > >
> > > Ed
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