This function automatically calls member functions on an interface, given the type information for the interface.
At a Glance
| Header file: | Oleauto.h |
| Windows CE versions: | 2.0 and later |
Syntax
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
Pointer to an implementation of the IDispatch interface described by ptinfo.
ptinfo
Pointer to the type information that describes the interface.
dispidMember
Identifies the member. Use GetIDsOfNames or the object’s documentation to obtain the DISPID.
wFlags
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
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 that contains exception information. This structure should be filled in if DISP_E_EXCEPTION is returned.
puArgErr
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
One of the values obtained from the returned HRESULT and described in the following table is returned.
| 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 into this function any invalid and, under some circumstances, NULL pointers will result in 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);
}