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List:       ms-atl
Subject:    [out] parameters
From:       Kevin Parkes <Kevin_Parkes () PENOP ! COM>
Date:       1998-02-27 9:03:50
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I have an object with a number of methods which create and return other
objects.
Some of these methods return the object through an [out,retval] parameter.
In other cases, because I wanted to return an error code on failure, I
tried
to return the object through an [out] parameter and the error code through
the [out,retval] parameter. Here is a simplified example:

interface IMyMainObj : IDispatch
{
     ...
     HRESULT Method1([out,retval] IMyOtherObj * * pObj );
     HRESULT Method2([out] IMyOtherObj * * pObj, [out,retval] short *
retval );
     ...
}

Both methods work fine in VB5. However in VBScript, Method1 works but
trying to call Method2 results in a "Type mismatch" error.

After searching the list archives and other resources, it seems I have two
alternatives:

1. Have Method2 return the object through an [out,retval] and return
   something like E_FAIL as the HRESULT on error.

2. Return the object in a Variant, as in:

     HRESULT Method2([out] VARIANT * pObj, [out,retval] short * retval );

Am I right? If so, what advantages or disadvantages does each alternative
have? Which would be the prefered alternative?

(By the way, I seem to recall seeing something about using [in,out], rather
than
just [out] for it to work in VB4, is that right?)

Thanks in advance,
Kevin

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