Re: How to pass a reference to a CComBSTR

>>> I'm passing in my CComBSTR like this: myfunction(& myCComBSTRvar)
>>> and myfunction looks like this:
>>> void myfunction(CComBSTR *myCComBSTRvarToUpdate) {}
>>
>> This is not passing by reference - you are passing pointers. To pass by
>> reference yous should declare myfunction as
>>
>> void myfunction(CComBSTR& myModifiableVariable)...
>>
>> and call it like
>>
>> myfunction(myCComBSTRvar);
>>

Very interesting. Is there any performance difference (or any practical
difference for that matter) between passing pointers vs. passing by
reference?

It looks like I have two approaches that both work. I am wondering which
one is better (faster performing and safer):

Approach A (passing by reference)

define function to pass by reference:
void myfunction(CComBSTR& myModifiableVariable)
and call like this:
myfunction(myCComBSTRvar);
and set the "return" (out) result like this at the end of myfunction:
CComBSTR tempCComBSTR(mySTLString.c_str());
myModifiableVariable = tempCComBSTR.Detach();

Approach B (passing by pointer)
define function to pass by pointer:
void myfunction(BSTR* myModifiableVariable) //cannot use CComBSTR in the
declaration but BSTR works
and call like this:
myfunction( & myCComBSTRvar);
and set the "return" (out) result like this at the end of myfunction:
CComBSTR tempCComBSTR(mySTLString.c_str());
*myModifiableVariable = tempCComBSTR.Detach();

Both approaches appear to work equally as well. Does one work better than
the other? Any performance difference? I suppose in this case passing by
reference is clearner because of the odd issue with CComBSTR not returning a
pointer and having to use BSTR.

On a related note, is it perfectly safe to pass a pointer to a CComBSTR
around as a BSTR, like shown in Approach B?

One final question if you will. What is the best way to convert a string
contained in an STL "string" variable type to a CComBSTR? For example,
currently I do this:
string mySTLString = "Hello";
CComBSTR tempCComBSTR(mySTLString.c_str());
myModifiableVariable = tempCComBSTR.Detach();

Is that an efficient way, or is there a better way?

Thanks again. You all have been a great help and I really appreciate it.

Steve


.

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