[Last Call] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

BSTR Problem!

Posted on 2001-06-13
18
Medium Priority
?
804 Views
Last Modified: 2013-11-20
Hi,

I am using an automation component which was developed by someone else?


After importing the corresponding *.tlb file,
the complier will genearte one *.tlh file which contain the following code!

__declspec(implementation_key(191))
HRESULT IFnVersionableDual::Checkout ( BSTR * CheckoutPath, _bstr_t Directory, _bstr_t FileName, const _variant_t & Options );

When I use the Checkout method,
I want to know how can I enter the paramter correctly.

I have tried this:

MyObject->Checkout("c:\\test.txt", "c:\\", "test.txt");

But it cannot be complied

The erros is cannot convert parameter 1 from 'char [1]' to 'unsigned short ** '.

How can I correct this problem?

Thanks!
0
Comment
Question by:cplau
  • 7
  • 3
  • 3
  • +3
18 Comments
 
LVL 2

Expert Comment

by:missionImpossible
ID: 6185040
use the _T()-macro:

MyObject->Checkout(
  _T("c:\\test.txt"),
  _T("c:\\"),
  _T( "test.txt")  );


0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6185045
use AllocSysString():

     CString str("Hockey is Best!");
     BSTR bstr = str.AllocSysString();

good luck
0
 
LVL 2

Expert Comment

by:missionImpossible
ID: 6185064
sorry, for the first parameter you should do the following:

_bstr_t CheckOutPath ( _T("c:\\test.txt") );

MyObject->Checkout(
 CheckOutPath,
 _T("c:\\"),
 _T( "test.txt")  );
0
Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

 

Expert Comment

by:SrinivasaRao
ID: 6185069
BSTR was defined as unsigned short* . So please use unsigned short** in the place of BSTR*. I hope this will solve your problem.
BSR
0
 
LVL 6

Expert Comment

by:snoegler
ID: 6185197
>>     CString str("Hockey is Best!");
>>    BSTR bstr = str.AllocSysString();

If you use this code, you have to add an ::SysFreeString(bstr); later!

Instead of allocating a BSTR this way, you can also

1. #include <afxpriv.h>
2. Place an USES_CONVERSION; as the first line of the function.
3. Use T2OLE() to convert from the TCHAR to BSTR/OLECHAR.

->
#include <afxpriv.h>

void doit()
{
USES_CONVERSION;
MyObject->Checkout(T2OLE(_T("c:\\test.txt")), T2OLE(_T("c:\\")), T2OLE(_T("test.txt")));
}
0
 

Author Comment

by:cplau
ID: 6185279
Hi All,

In the tlh file, I also found this code,
 __declspec(property(get=GetNumber))
    _bstr_t Number;

When I try to read this object's properties like this

MyObject->Number

Do I need to do any coversion to get the correct value?

Thanks!
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6185295
i still think that it better that u maintain your allocation and free instead of rely on the systme

0
 
LVL 2

Expert Comment

by:missionImpossible
ID: 6185296
_bstr_t is a wrapper-class for BSTR, so you can read the Number-property like you suggest. There is no conversion needed.
0
 
LVL 9

Expert Comment

by:ShaunWilde
ID: 6185375
first of all is CheckoutPath an [in],[out],[in,out] parameter - what is in the idl?

this will determine how we deal with it - because it is a BSTR* then I suspect it is an [out] or [in,out] - however it could have just been defined incorrectly

if [out]

_bstr_t bstrCheckout;
MyObject->Checkout(&bstrCheckout, "c:\\", "test.txt");

if [in,out]
_bstr_t bstrCheckout(_T("c:\\test.txt"));
MyObject->Checkout(&bstrCheckout, _T("c:\\"), _T("test.txt"));

I hope this helps



0
 
LVL 9

Expert Comment

by:ShaunWilde
ID: 6185390
however you may have to do it like this if _bstr_t doesn't support & operator to return a pointer to its internal BSTR (which I know CComBSTR does)

if [out]

BSTR bstrCheckout=NULL;
MyObject->Checkout(&bstrCheckout, "c:\\", "test.txt");

::SysFreeString(bstrCheckout);


if [in,out]
BSTR bstrCheckout=::SysAllocString(T2W((_T("c:\\test.txt"))));
MyObject->Checkout(&bstrCheckout, _T("c:\\"), _T("test.txt"));

::SysFreeString(bstrCheckout);
0
 

Author Comment

by:cplau
ID: 6185438
Dear All,

At my first question,

__declspec(implementation_key(191))
HRESULT IFnVersionableDual::Checkout ( BSTR * CheckoutPath, _bstr_t Directory, _bstr_t FileName, const
_variant_t & Options );

The fourth paramter is the optional paramter

CString str("c:\\yyee.txt");
BSTR bstr = str.AllocSysString();
CString str1("c:\\");
BSTR bstr1 = str1.AllocSysString();
CString str2("yyee.txt");
BSTR bstr2 = str2.AllocSysString();

COleVariant name(1);

Temp->Checkout(&bstr,bstr1,bstr2,name);

But the following error :
COleVariant::COleVariant' : ambiguous call to overloaded function

I've also tried using this
ColeVairant name("%d", 1);

But the program crash while running!

What mistake had I made?
How can I input the fourth parameter with a value of 1?

Thanks!
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6185633
cplau: initialaize the 'name' like this:

COleVariant name(1.0);

and it will work... :)
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6185634
cplau: initialaize the 'name' like this:

COleVariant name(1.0);

and it will work... :)
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6185648
or even better:

     COleVariant name((short)1); !!!

since there's no constructor for int...

cheer
0
 
LVL 9

Accepted Solution

by:
ShaunWilde earned 600 total points
ID: 6186161
remember to free your BSTRs that you allocated or else it will leak

CString str("c:\\yyee.txt");
BSTR bstr = str.AllocSysString();

// your code


::SysFreeString(bstr);


> COleVariant::COleVariant' : ambiguous call to overloaded function

use COleVariant name((short)1); // for VT_I2
or COleVariant name((long)1); // for VT_I4
or COleVariant name(1,VT_I2);
or COleVariant name(1,VT_I4);

> ColeVairant name("%d", 1);
COleVariant does not do string formatting - you were telling the variant that the string being passed in was actually a VT_NULL




0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6190149
great, using my comment to get the points
0
 
LVL 6

Expert Comment

by:snoegler
ID: 6190180
Isn't this the point there was a quite lengthy discussion about a short time ago?
:-/
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 6190581
whatever
0

Featured Post

Independent Software Vendors: 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

In this post we will learn different types of Android Layout and some basics of an Android App.
Ready to get certified? Check out some courses that help you prepare for third-party exams.
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.
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an anti-spam), the admin…
Suggested Courses

834 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