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DispInvoke
_this, ptinfo, dispidMember, wFlags, pparams, pvarResult, pexcepinfo, puArgErr)
void FAR* _this
ITypeInfo FAR* ptinfo
DISPID dispidMember
unsigned short wFlags
DISPPARAMS FAR* pparams
VARIANT FAR* pvarResult
EXCEPINFO pexcepinfo
unsigned int FAR* puArgErr
Automatically calls member functions on an interface, given type information
for the interface. You can describe an interface with type information and
implement IDispatch::Invoke for the interface using this single call.
Parameters
_this
Pointer to an implementation of the IDispatch interface described by ptinfo.
ptinfo
Pointer to the type information describing the interface.
dispidMember
Identifies the member. Use GetIDsOfNames or the object's documentation to obtain the dispatch ID.
wFlags
Flags describing the context of the Invoke call, as follows:
Value
| Description
| DISPATCH_METHOD
| The member is being invoked as a method. If a property has the same name, both
this and the DISPATCH_PROPERTYGET
flag may be set.
| DISPATCH_PROPERTYGET
| The member is being retrieved as a
property or data member.
| DISPATCH_PROPERTYPUT
| The member is being changed as a
property or data member.
| DISPATCH_PROPERTYPUTREF
| The member is being changed via a reference assignment, rather than a
value assignment. This flag is valid
only when the property accepts a
reference to an object.
|
pparams
Pointer to a structure containing an array of arguments, an array of argument
dispatch IDs for named arguments, and counts for number of elements in the
arrays.
pvarResult
Pointer to where the result is to be stored, or NULL if the caller expects no result. This argument is ignored if
DISPATCH_PROPERTYPUT or DISPATCH_PROPERTYPUTREF is specified.
pexcepinfo
Pointer to a structure containing exception information. This structure should be filled in if DISP_E_EXCEPTION is returned.
puArgErr
The index within rgvarg of the first argument that has an error. Arguments are stored in pdispparams->rgvarg in reverse order, so the first argument is the one with the highest index in
the array. This parameter is returned only when the resulting SCODE is
DISP_E_TYPEMISMATCH or DISP_E_PARAMNOTFOUND.
Return Value
The SCODE obtained from the returned HRESULT is one of the following:
SCODE
| Meaning
| S_OK
| Success.
| DISP_E_BADPARAMCOUNT
| The number of elements provided in DISPPARAMS is different from the number of
arguments accepted by the method or property.
| DISP_E_BADVARTYPE
| One of the arguments in DISPPARAMS is not a valid variant type.
| DISP_E_EXCEPTION
| The application needs to raise an exception. In this case, the structure
passed in pexcepinfo should be filled in.
| DISP_E_MEMBERNOTFOUND
| The requested member does not exist.
| DISP_E_NONAMEDARGS
| This implementation of IDispatch does not support named arguments.
| DISP_E_OVERFLOW
| One of the arguments in DISPPARAMS could not be coerced to the specified type.
| DISP_E_PARAMNOTFOUND
| One of the parameter IDs does not correspond to a parameter on the method. In
this case puArgErr is set to the first argument that contains the error.
| DISP_E_PARAMNOTOPTIONAL
| A required parameter was omitted.
| DISP_E_TYPEMISMATCH
| One or more of the arguments could not be coerced. The index within rgvarg of the first parameter with the incorrect type is returned in puArgErr.
| E_INVALIDARG
| One of the arguments is invalid.
| E_OUTOFMEMORY
| Insufficient memory to complete operation.
| Other returns
| Any of the ITypeInfo::Invoke errors may also be returned.
|
Comments
The parameter _this is a pointer to an implementation of the interface being deferred to. DispInvoke builds a stack frame, coerces parameters using standard coercion rules,
pushes them on the stack, and calls the correct member function in the virtual
function table (VTBL).
Example
The following code from the Lines sample file LINES.CPP implements IDispatch::Invoke using DispInvoke. This function uses m_bRaiseException to signal that an error occurred during the DispInvoke call.
STDMETHODIMP
CLines::Invoke(
DISPID dispidMember,
REFIID riid,
LCID lcid,
WORD wFlags,
DISPPARAMS FAR* pdispparams,
VARIANT FAR* pvarResult,
EXCEPINFO FAR* pexcepinfo,
UINT FAR* puArgErr)
{
HRESULT hr;
if (NULL == pexcepinfo)
return ResultFromScode(E_INVALIDARG);
m_bRaiseException = FALSE;
hr = DispInvoke(
this, m_ptinfo,
dispidMember, wFlags, pdispparams,
pvarResult, pexcepinfo, puArgErr);
if (m_bRaiseException)
{
_fmemcpy(pexcepinfo, &m_excepinfo, sizeof(EXCEPINFO));
return ResultFromScode(DISP_E_EXCEPTION);
}
else return hr;
}
See Also
CreateStdDispatch, IDispatch::Invoke
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