Copy constructor of unkown TObject delivered class

[dwielane]

Hi,
is there some way to call copy constructor of any TObject based class? I know that I can use TClass for calling default constructor but I have know idea is this is possible to call copy constructor in such way.
Unfortunately I cannot use Clone method.

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ROOT Version (e.g. 6.08):
Platform, compiler (e.g. Min 17, gcc4.8):

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[Danilo]

Hi,

I think it’s not possible to use TClass to invoke a particular copy constructor. Note that TClass lets you access the representation of all classes known to the type system, not only the ones inheriting from TObject.

Can I help you out nevertheless? What are you trying to achieve?

Cheers,
D

[dwielane]

Hi,
I have class that I need to copy however my copy constructor do init-like stuff so I suppose using Clone will not help (because this make copy of my object).
Actually I can just do something like this:
BaseCopy *copy = (BaseCopy)myObj->Clone();
copy->Overwrite(myObj);
It’s just less “nice” approach.

[Wile_E_Coyote]

If you inherit from TObject (or TNamed), you can implement you own Clone and/or Copy methods (they’re “virtual”).

[pcanal]

To copy an TObject (or a class derived from), you can call the ‘default’ (usually no need to overload) Clone:

MyClass *myobject = ....;
MyClass *mycopy = dynamic_cast<MyClass *>(myobject->Clone());

This will use the I/O sub-system to copy the object (one important consequence is that transient data member are not copied but left with the value given by the default constructor).

Cheers,
Philippe.

[pcanal]

If you need to ‘update’ an existing object rather than using Clone (which allocates) it, then you can try (to write a small wrapper function that does)

     TBufferFile buffer(TBuffer::kWrite,bufsize);
     buffer.MapObject(obj);  //register obj in map to handle self reference
     input->Streamer(buffer);
     // here some additional compliciation needed if you use TRef  in conjunction with those objects.

      // read new object from buffer
      buffer.SetReadMode();
      buffer.ResetMap();
      buffer.SetBufferOffset(0);

      buffer.MapObject(newobj);  //register obj in map to handle self reference
      newobj->Streamer(buffer);
      newobj->ResetBit(kIsReferenced);
      newobj->ResetBit(kCanDelete);

Cheers,
Philippe.