RE: [ROOT] Root I/O and object deletion

From: Philippe Canal (pcanal@fnal.gov)
Date: Tue Apr 29 2003 - 18:19:00 MEST 

Hi Thomas,

One solution is to use (instead of (re)setBit) a transient data member. For
example.

class A : public TObject {
    TNamed *fNamed;
    bool fOwner;    //! true if we own the TNamed object
    A() : fNamed(0),fOwner(true);
    ~A() { if (fOwner) delete fNamed; }
    void SetName(const char *name) { if (fOwner) delete fNamed; fNamed = new
TNamed(name, ""); fOwner = true; }
    void SetName(TNamed *name) { if (fOwner) delete fNamed; fNamed = name;
fOwner = false; }
    ClassDef(A, 1);
};

The only draw back is that if the 'A' object is re-used (instead of being)
re-constructed, fOwner might be incorrect.

Cheers,
Philippe

-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Thomas Bretz
Sent: Tuesday, April 29, 2003 8:14 AM
To: roottalk@pcroot.cern.ch
Subject: [ROOT] Root I/O and object deletion


Dear rooters,

here is a simplified example to illustrate my question: If I have a class

class A : public TObject {
    TNamed *fNamed;
    ~A() { if (TestBit(BIT(14)) delete fNamed; }
    void SetName(const char *name)
    { fNamed = new TNamed(name, ""); SetBit(BIT(14)); }
    vodi SetName(TNamed *name) { fNamed = name; ResetBit(BIT(14)); }
    ClassDef(A, 1)
}

and now I create an instance of this class
A a, b;
a.SetName(new TNamed);
b.SetName("NewName");

and write both objects to a file:
a.Write("Obj1");
b.Write("Obj2");

now I read this object into new objects:
A c,d;
c.Read("Obj1");
d.Read("Obj2");

As I understand it, now both objects (c and d) have a newly allocated
TNamed. But for one of the two objects BIT(14) is set and for one not.
How can I make sure, that the destruction of the TNamed-data-member is
done correctly in any case?

Thanks in advance,
Thomas.

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