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Variant String Problems

Posted on 2002-03-17
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Last Modified: 2010-04-02
Hi,

I am using Borland C Builder 5. I am trying to create a custom collection class, but I am having
problems with strings and variants. My add method takes in a TVariant*
which I then copy into a global TVariant using the VariantCopy method
(after using the VariantInit method on the global TVariant). When I
return it, I simply return a pointer to the global TVariant. The problem
is when the variant contains a string. Supposedly the VariantCopy method
copies the string however this does not appear to be happening. From a
VB client, if I access the value from the same function as I added it, I
get the right string, but if I access it from another function, where
the string is out of scope, I get a different string. What am I doing
wrong??

Thanks,

Zaphod.
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Question by:Z_Beeblebrox
4 Comments
 

Expert Comment

by:assermark
ID: 6876380
First, COM-support in BCB5 suffering from some serious bugs. If you intend do do some COM-programming in in BCB, and particular if your clients is not written in BCB, you should upgrade to ver.6, where (among other things) TVariant is exchanged to the VARIANT-structure.

In COM a client always should deallocate a returned string, and that is what your VB-client is doing. For that reason your server should return a copy, not a pointer to your local storage.

If you post some sourcecode it´s maby easyer to solve your problem.
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Author Comment

by:Z_Beeblebrox
ID: 6878994
I figured it out, I was passing a pointer to the global variant and VB was changing it. So now I pass it a new variant.

Zaphod.
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LVL 49

Expert Comment

by:DanRollins
ID: 7085365
Hi Z_Beeblebrox,
You've requested to delete this question, but its status remains as 'Pending Delete' because one or more comments have been added.  Normally, the only way to fully delete such a Question is to post a message to Community Support and ask for assistance.

EE is making a one-time database sweep to purge the Pending Delete Questions automatically.  During this sweep:

    Z_Beeblebrox -- To allow the deletion to proceed:  Do nothing.
    EXPERTS -- Please DON'T POST a comment except to contest this deletion.

In the future, please refer to http://www.experts-exchange.com/jsp/cmtyHelpDesk.jsp#8 for instruction on deleting questions.

DanRollins -- EE database cleanup volunteer
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Accepted Solution

by:
Moondancer earned 0 total points
ID: 7104565
100 points refunded, moved to the PAQ and closed rather than deleted, since you added the solution and it may help others.
Moondancer - EE Moderator
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