Solved

Passing VB arrays from C...

Posted on 1999-01-12
5
171 Views
Last Modified: 2010-05-03
Hello. I am trying to use an OCX written specifically for use with VB. Some of the parameters require a VB array to be passed. Of course, VB array are completely different than in C. Is there any api for handling VB type arrays ? I have tried using the Safe Array functions in the Microsoft Developer Studio 5.0 (e.g. safeArrayCreate) with no success. I'm not even sure this is the same thing ! Help...!
0
Comment
Question by:gburson
  • 3
  • 2
5 Comments
 
LVL 4

Expert Comment

by:chabaud
ID: 1455631
Your are on the right way, your must use SAFEARRAY.
Here is an C++ sample using atl which create an array of variants:

STDMETHODIMP CClass::Test( VARIANT* retpsa)
{
hResult = S_OK;
SAFEARRAY FAR* psa;
SAFEARRAYBOUND rgsabound[2];
VARIANT HUGEP *pvar;
int i, idx;

rgsabound[0].lLbound = 0;
rgsabound[0].cElements = nRow-1;

rgsabound[1].lLbound = 0;
rgsabound[1].cElements = nCol-1;

psa = SafeArrayCreate(VT_VARIANT, 2, rgsabound);
if (psa == NULL)
      {
      hResult = HERROR | ERR_ALLOCATING_VARIANT;
      goto End;
      }

hResult = SafeArrayAccessData(psa, (void HUGEP* FAR*)&pvar);
if (FAILED(hResult))
      {
      hResult = HERROR | ERR_ACCESS_VARIANT;
      goto End;
      }

for (int i = 0; i < nRow; i++)
      {
        idx = i;

      pvar[idx].vt = VT_BSTR;
      pvar[idx].bstrVal = _bstr_t("some data").copy();

      idx += nRow;
      pvar[idx].vt = VT_I4;
      pvar[idx].lVal = (long)123;
      }

SafeArrayUnaccessData(psa);

VariantInit(retpsa);
retpsa->vt = VT_ARRAY | VT_VARIANT;
retpsa->parray = psa;

End:
SafeArrayDestroy(psa);

return 0;
}

0
 

Author Comment

by:gburson
ID: 1455632
Thanks Chabaud. Just to clarify - I believe the OCX expects dynamic arrays. Does this change the answer ?

Thank again.
0
 
LVL 4

Expert Comment

by:chabaud
ID: 1455633
My sample just return a two dimension safe array.

But you can get array in also. The import function is SafeArrayAccessData which allow you to access array element in C.
0
 

Author Comment

by:gburson
ID: 1455634
One last question - I will be coding in C, so to allocation the bstr, should I use sysAllocString ? Any other problems ?

Also I how do I close/grade this question !

Thankyou,
Glen.
0
 
LVL 4

Accepted Solution

by:
chabaud earned 200 total points
ID: 1455635
Yes you can use SysAllocString and SysFreeString to handle BSTR.

In C++ the built-in _bstr_t class is a very helpfull wrapper for this BSTR function.
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

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

Have you ever wanted to restrict the users input in a textbox to numbers, and while doing that make sure that they can't 'cheat' by pasting in non-numeric text? Of course you can do that with code you write yourself but it's tedious and error-prone …
A theme is a collection of property settings that allow you to define the look of pages and controls, and then apply the look consistently across pages in an application. Themes can be made up of a set of elements: skins, style sheets, images, and o…
Get people started with the process of using Access VBA to control Excel using automation, Microsoft Access can control other applications. An example is the ability to programmatically talk to Excel. Using automation, an Access application can laun…
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlin…

914 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

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now