Dear Rene
Thank you for the fast reply and especially for the implementation
of TDirectory::FindObjectAny().
Please let me comment to your answers of my questions to see if my
code has some flaws:
1, Constructor: As far as I understand "gDirectory->FindObject(name)"
does only find an object if it is already in memory. So in order to
check if a directory exists in a TFile stored on disk, I did:
"key = fDir->GetKey(obj->GetName());"
If (key != 0) then the directory does exist. Is this correct?
2, RecursiveRemove: What I wanted to do is "fDir->Delete(obj)" in
order to delete an object permanently from TFile on disk.
I am not sure if "fDir->Delete(obj-GetName())" does delete the object
permanently, since "obj-GetName()" does not return the namecycle,
since the object is in memory?
How can I delete an object permanently from a TFile on disk, when
the object is loaded into memory already?
5, EncodeNameCycle: I need to get "key = fDir->GetKey(name,cycle);",
so I have written my own function to extract name and cycle, but I
thought it would be easier if TObject would already contain this
possibility.
Best regards
Christian
Rene Brun wrote:
> Hi Christian,
>
> On Fri, 4 Jan 2002, cstrato@EUnet.at wrote:
>
> > Dear Rene;
> >
> > When trying to create a complicated directory hierarchy in TFile, I came
> >
> > across the following questions:
> >
> > 1, Constructor: Sorrowly, mkdir() cannot be used to check if a directory
> >
> > exists already, since "Error("TDirectory","Directory %s exists
> > already",name);"
> > in the constructor does not set "gDirectoy = 0;". I suppose this is a
> > feature to allow namecycles, but then I would suggest to change "Error"
> > to "Warning"?
> >
> You can check if name (object or directory) is already in the current dir
> with gDirectory->FindObject(name).
>
> > 2, RecursiveRemove(): Is it ok to call RecursiveRemove(), when I want to
> >
> > delete a TObject, or does this have side effects? (I need to pass a
> > TObject and not a namecycle.)
>
> Why do you want to call RecursiveRemove? This function is automatically
> by the TObject destructor when object->TestBit(kMustCleanup) is true.
> The kMustCleanup bit is automatically set for objects added to TPad
> and TFolder. You can set this bit yourself object->SetBit(kMustCleanup)
> if you want this object to be automatically removed from all containers
> referencing it when the object is deleted.
> You can add a container to teh list of containers to be cleaned via
> gROOT->GetListOfCleanups()->Add(mycollection);
>
> >
> > 3, Write(): Is there a reason why the variable "name" is not used in
> > method
> > Write(name = 0,..)? It would be great if I could use dir->Write(MyName)
> > to
> > write a single object to TFile.
>
> You better use object->Write();
> or object->Write(name);
>
> This will write object into the current directory. By default, if you do
> not specify a name, the object name is used. If you specify the parameter
> name, this will be the name of the key.
>
> > > 4, FindObjectAny(): How can I
> find an object in TFile containing a > complicated
> > hierarchy of TDirectories? It would be great to have a recursive method
> > analogous to "TFolder::FindObjectAny()".
>
> I will implement FindObjectAny. This was not implemented because in case
> of a complex directory structure, this call will force reading all
> directory keys in memory. But, I agree that there are more advantages
> than disadvantages in implementing FindObjectAny.
>
> >
> > 5, EncodeNameCycle(): Since every TObject can be stored in TFile, would
> > it
> > be possible to move the methods Encode/DecodeNameCycle() to TObject?
>
> Why do you need this ?
> See object->Write
>
> >
> > 6, Shortcut/Alias: A nice feature of TFolder is that one folder can be
> > added to different folders. It would be great if this could also be done
> >
> > with TDirectory, e.g. as shortcut or alias as known from other file
> > systems.
> > Sorrowly, creating a reference TRef does not help, since TBrowser is not
> >
> > able to recognize it as alias to TDirectory.
>
> Unix-like links are not implemented in TDirectory. This could be added
> to the current TKey or a new class TKeyLink implemented.
>
> Rene Brun.
>
> >
> > Thank you for your help.
> >
> > Best regards
> > Christian
> > ----------------------------------
> > C.h.r.i.s.t.i.a.n S.t.r.a.t.o.w.a
> > V.i.e.n.n.a, A.u.s.t.r.i.a
> >
> >
> >
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