Hi THomas, what do you mean with the contents of A is not written to the file. If B derives from A and you write B then both B and the base class A are written to file. This assuming that you don't use a hand coded streamer. So if later you change the schema of A you have to update the classdef version number since it is a new schema. However, the system will be able to continue to read objects written in schema version N and N+1 (or N=M). Cheers, Fons. On Fri, 2002-08-02 at 12:35, Thomas Bretz wrote: > Hi, > > I have a class A derived from class B. class A is defined with > ClassDef(A, 1). Class B with ClassDef(B, 0). > Now I write class A to a file and get what I expected. The information > from class A is written to the file, while the information from class B > is skipped. Now I changed the contents of class B and get a warning > about the checksum for class B when reading from an 'old' file. What is > the meaning of checking the checksum of a class which contents are not > written to a file? What shell I do? The proposal of root is to increase > the Version number by one... Which is really not what I want. > > Regards, > Thomas. -- Org: CERN, European Laboratory for Particle Physics. Mail: 1211 Geneve 23, Switzerland E-Mail: Fons.Rademakers@cern.ch Phone: +41 22 7679248 WWW: http://root.cern.ch/~rdm/ Fax: +41 22 7679480
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