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Converting data types (again)...

Posted on 1999-01-20
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Last Modified: 2013-11-25
I have this function in some .h file included in my ATL COM program:

function(char *);

and need to pass this variable in the ATL COM code into the "char *" part of the above function:

BSTR SomeData;

How do I do that?

So, I need to call this function in my ATL COM code like this:

BSTR SomeData;

// Conver BSTR to char (what is the code needed here)

function(charOfSomeData);

Thanks...
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Question by:loyaliser
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Accepted Solution

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chensu earned 80 total points
ID: 1184667
You can make use of _bstr_t class that comes with Visual C++ 5.0 or later, which you are likely using since you are using ATL.

#include <comdef.h>

BSTR SomeData;

_bstr_t bstrData(SomeData, true);

function(bstrData);


This is because _bstr_t class overloads the operator char*.

operator char*( ) const throw( _com_error );

You should also handle the exception that might be thrown using try-catch in the above code.
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by:loyaliser
ID: 1184668
I will give it a try tomorrow morning... thanks...
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Author Comment

by:loyaliser
ID: 1184669
I hope you don't mind, but what would be the code for doing it the other way around... char [] to BSTR?

Thanks...
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Expert Comment

by:chensu
ID: 1184670
Use the ATL conversion macro A2BSTR.

USES_CONVERSION;
A2BSTR();

Or, simply use _bstr_t since it has a constructor

_bstr_t( const char* s2 ) throw( _com_error );

and use _bstr_t in place of BSTR.

You may also use CComBSTR class in ATL.
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