DispInvoke

Article
06/30/2006

This function automatically calls member functions on an interface, given the type information for the interface.

HRESULT DispInvoke(
  void FAR* _this, 
  ITypeInfo FAR* ptinfo, 
  DISPID dispidMember, 
  unsigned short wFlags, 
  DISPPARAMS FAR* pparams, 
  VARIANT FAR* pvarResult, 
  EXCEPINFO pexcepinfo, 
  unsigned int FAR* puArgErr 
);

Parameters

_this
[in] Pointer to an implementation of the IDispatch interface described by ptinfo.
ptinfo
[in] Pointer to the type information that describes the interface.
dispidMember
[in] Identifies the member. Use IDispatch::GetIDsOfNames or the object's documentation to obtain the DISPID.

wFlags
[in] Flags describing the context of the Invoke call, as follows.

Value	Description
DISPATCH_METHOD	The member is invoked as a method. If a property has the same name, both this and the DISPATCH_PROPERTYGET flag can be set.
DISPATCH_PROPERTYGET	The member is retrieved as a property or data member.
DISPATCH_PROPERTYPUT	The member is changed as a property or data member.
DISPATCH_PROPERTYPUTREF	The member is changed by 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 that contains an array of arguments, an array of argument DISPIDs for named arguments, and counts for number of elements in the arrays.
pvarResult
[out] 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
[out] Pointer to a structure that contains exception information.This structure should be filled in if DISP_E_EXCEPTION is returned.
puArgErr
[out] 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 return value is DISP_E_TYPEMISMATCH or DISP_E_PARAMNOTFOUND.

Return Values

The following table shows the HRESULT values that can be returned by this function.

Value	Description
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 of the first parameter with the incorrect type within rgvarg is returned in puArgErr.
E_INVALIDARG	One of the arguments is invalid.
E_OUTOFMEMORY	Insufficient memory to complete the operation.
Other return codes	Any of the ITypeInfo::Invoke errors can also be returned.

Remarks

The parameter this is a pointer to an implementation of the interface that is being deferred to. DispInvoke builds a stack frame, coerces parameters using standard coercion rules, pushes them on the stack, and then calls the correct member function in the VTBL.

Passing invalid (and under some circumstances NULL) pointers to this function causes an unexpected termination of the application.

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)
{
  return DispInvoke(this,
                    m_ptinfo,
                    dispidMember, 
                    wFlags, 
                    pdispparams,
                    pvarResult,
                    pexcepinfo, 
                    puArgErr); 
}

Requirements

OS Versions: Windows CE 2.0 and later.
Header: Oleauto.h.
Link Library: Oleaut32.lib.

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