PRB: Wrapper Class for Automation Object May Be Incomplete (152073)
The information in this article applies to:
- The ClassWizard, when used with:
- Microsoft Visual C++, 32-bit Editions 2.0
- Microsoft Visual C++, 32-bit Editions 2.1
- Microsoft Visual C++, 32-bit Editions 2.2
- Microsoft Visual C++, 32-bit Editions 4.0
- Microsoft Visual C++, 32-bit Editions 4.1
This article was previously published under Q152073 SYMPTOMS
An automation object may support a statement and function with the same
name even though the statement and function will most likely have different
behaviors. Class Wizard will not recognize both the statement and function.
However, when generating a new class from the object's type library, the
Class Wizard will generate a function and prototype for a single function.
This generated function will not give you the ability to call both the
function and the statement.
CAUSE
The similarly-named function and statement will share a single entry in the
.odl file for the object and a single entry in the type library. The Class
Wizard does the best job it can and generates a single function and
prototype based on this entry.
RESOLUTION
Given adequate documentation for the statement and function, it is possible
to modify the wrapper class by hand so that the statement or function may
be called. If the parameter list for the statement and function vary, which
may be the case if optional parameters are used, the wrapper function can
be overridden. Otherwise, the wrapper for the statement and function will
need different names.
STATUS
This behavior is by design.
MORE INFORMATION
An example of this problem is WordBasic's Bold. The Bold statement turns
the bold character formatting on and off just as selecting the Bold Toolbar
button in Word does. The Bold() function returns a short indicating whether
all, some, or none of the characters in a selection are formatted as bold.
Visual Basic will call the function if a return value is assigned to the
Bold() call. Otherwise, it will call the Bold statement.
The .odl statement for Bold is as follows:
[id(0x00008048), helpstring("Makes the selection bold (toggle)"),
helpcontext(0x00001d48)] short Bold([in, optional] VARIANT On);
The Class Wizard will generate the following function and prototype using
this information:
short Bold(const VARIANT& On);
short WordBasic::Bold(const VARIANT& On)
{
short result;
static BYTE parms[] =
VTS_VARIANT;
InvokeHelper(0x8048, DISPATCH_METHOD, VT_I2, (void*)&result, parms,
&On);
return result;
}
Using this function will result in the WordBasic Bold() function being
called. In order to call the statement, you could define BoldStatement()
and BoldFunction() functions. In this case, however, because there is no
reason to pass a parameter to the Bold() function, the parameter lists vary
and it is possible to overload the wrapper functions as follows:
void Bold(const VARIANT& On);
short Bold();
void WordBasic::Bold(const VARIANT& On)
{
static BYTE parms[] =
VTS_VARIANT;
InvokeHelper(0x8048, DISPATCH_METHOD, VT_EMPTY, NULL, parms,
&On);
}
short WordBasic::Bold()
{
short result;
static BYTE parms[] =
VTS_VARIANT;
InvokeHelper(0x8048, DISPATCH_METHOD, VT_I2, (void*)&result, NULL);
return result;
}
REFERENCES
Microsoft Office Developer's Kit - PART 2 Word Basic Reference,
Statements and Functions.
| Modification Type: | Major | Last Reviewed: | 10/24/2003 |
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| Keywords: | kbAutomation kbprb KB152073 |
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