alanglloyd

In article <zGqYa.11809$os2.174837@news2.e.nsc.no>, "Bjørge Sæther"
<bjorge@hahaha_itte.no> writes:

_Any_ data file should have a version number (or major and minor version
numbers) embedded in the first bytes of the data file. Then if you need an
update you can read as the old version, and write as the new.

That, of course, is if that sort of operation makes sense. For some changes you
cannot even do that.

Alan Lloyd
alanglloyd@aol.com

bjørge sæther

"AlanGLLoyd" <alanglloyd@aol.com> skrev i melding
news:20030811032506.23406.00001365@mb-m27.aol.com...

?


Agreed. When using record type files, this means you'll ahve to declare a
new record type for each change. And - write a conversion routine that takes
data from the old to the new type. At that point, I believe the "easiness"
of typed records has gone down the drain, and putting the effort into
writing a dynamic storage mechanism would be better.


changes you


No, then one may need a migration application or whatever to deal with it.
But that's the same with all storage formats.

--
Regards,

Bjørge Sæther
bjorge@haha_itte.no
-------------------------------------
I'll not spend any money on American Software products
until armed forces are out of Iraq.

geir_baardsen

Ok. I'll give it a try...

bjørge sæther

"Bruce Roberts" <ber@bounceitattcanada.xnet> skrev i melding
news:yGPZa.61$0I.2941@news20.bellglobal.com...

I meant 'dynamic' as opposed to 'static' Record Type Files. To me, storing
data in a database counts for 'dynamic'. It's not the best term, though...

--
Regards,

Bjørge Sæther
bjorge@haha_itte.no
-------------------------------------
I'll not spend any money on American Software products
until armed forces are out of Iraq.

alf christophersen

Use class nd streams and remember to define a base class from which
all classes derive. Declare a version datafield and store it in the
SavetoStream procedure. Use the version info to test whether another
field should be loaded or not. In that way you never to convert from
one record to another :-) Remember to use tPersistent as base for the
base class. Otherwise you get problems using tStream.

marco van de voort

Hmm. Small tools and reading/processing/writing existing file structures.