Re: When to use Clear() versus Delete()

From: Fons Rademakers (Fons.Rademakers@cern.ch)
Date: Wed Oct 01 1997 - 21:23:17 MEST 

Hi David,

In general: 
  - when you have a collection "owning" the objects use Delete().
    This will delete the objects and clear the collection.

  - when a collection stores "references" (i.e. the objects
    are "owned" by a different collection or some pointer
    array), use Clear(). This clears the collection, but does
    not delete the object.

Since TClonesArrays always own the objects use Delete().

However, TClonesArrays are special in that they not really
delete the object space, TClonesArray::Delete() only makes sure
the destructors of the objects are called properly.

David Nitz wrote:
> 
> I'm fairly new to trying to use root and C++.  I'm trying to set up
> an event structure similar to the examples using TClonesArray.
> 
> I've gone over this a number of times, but remain confused about when
> I should use "Clear" and when I should use "Delete" to prepare storage
> for a new event.  Can anyone explain the difference to me?  Thanks.
> 
> David F. Nitz  (dfnitz@umich.edu)
> Physics Department, University of Michigan

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