Solved

COM: Returning a string from a method

Posted on 2001-07-02
2
338 Views
Last Modified: 2013-11-20
Hi,

I am writing an ActiveX control for use with Automation.
But now I am stuck (again).

All I simply want to do is to create a string (A BSTR I assume) and return it from my ActiveX method to the caller. How do I do that (the correct way)?

If I allocate memory for the string using SysAllocString() and then return that pointer is it then the responsibility of the caller to deallocate it, or must the callee do that somehow? I would guess that it was the responsibility of the caller since this is the case with AddRef/Release.

PS: I already know all about converting between BSTR/Unicode/ANSI - it is the allocation/deallocation that I am concerned about.

Jacob Marner, B.Sc.
0
Comment
Question by:felonius
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 2

Accepted Solution

by:
dhodge earned 100 total points
ID: 6245634
Releasing the memory is the task of the calling code.  Alternatively just use one of the BSTR wrapper classes in your calling code then it will automatically release the memory.
0
 
LVL 12

Expert Comment

by:migel
ID: 6245668
Hi!
you can write like this:

HRESULT CMyControl::GetSTring(BSTR* pbstr)
{
_bstr_t str("This is a test!");
*pbstr = str.copy();
 return S_OKAY;
}
Caller must free this string  - COM convention.
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

In this article, I'll describe -- and show pictures of -- some of the significant additions that have been made available to programmers in the MFC Feature Pack for Visual C++ 2008.  These same feature are in the MFC libraries that come with Visual …
Introduction: Dynamic window placements and drawing on a form, simple usage of windows registry as a storage place for information. Continuing from the first article about sudoku.  There we have designed the application and put a lot of user int…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.

756 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question