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This function retrieves a parameter from the DISPPARAMSstructure, checks both named parameters and positional parameters, and coerces the parameter to the specified type.
HRESULT DispGetParam( DISPPARAMS FAR * pdispparams, unsigned int position, VARTYPE vtTarg, VARIANT FAR * pvarResult, unsigned int FAR * puArgErr );
Parameters
Return Values
One of the values obtained from the returned HRESULTand described in the following table is returned.
Value | Description |
---|---|
S_OK | Success. |
DISP_E_BADVARTYPE | The variant type vtTargis not supported. |
DISP_E_OVERFLOW | The retrieved parameter could not be coerced to the specified type. |
DISP_E_PARAMNOTFOUND | The parameter indicated by positioncould not be found. |
DISP_E_TYPEMISMATCH | The argument could not be coerced to the specified type. |
E_INVALIDARG | One of the arguments was invalid. |
E_OUTOFMEMORY | Insufficient memory to complete operation. |
Remarks
The output parameter pvarResultmust be a valid variant. Any existing contents are released in the standard way. The contents of the variant are freed with VariantFree.
Passing into this function any invalid and, under some circumstances, NULL pointers will result in unexpected termination of the application.
If you have used DispGetParamto get the right side of a property put operation, the second parameter should be DISPID_PROPERTYPUT. For example:
DispGetParam(&dispparams, DISPID_PROPERTYPUT, VT_BOOL, &varResult)
Named parameters cannot be accessed positionally, and vice versa.
Example
The following code example uses
DispGetParamto set
X
and
Y
properties:
STDMETHODIMP CPoint::Invoke( DISPID dispidMember, REFIID riid, LCID lcid, unsigned short wFlags, DISPPARAMS FAR* pdispparams, VARIANT FAR* pvarResult, EXCEPINFO FAR* pExcepInfo, unsigned int FAR* puArgErr) { unsigned int uArgErr; HRESULT hresult; VARIANTARG varg0; VARIANT varResultDummy; UNUSED(lcid); UNUSED(pExcepInfo); // Make sure the wFlags are valid. if(wFlags & ~(DISPATCH_METHOD | DISPATCH_PROPERTYGET | DISPATCH_PROPERTYPUT | DISPATCH_PROPERTYPUTREF)) return ResultFromScode(E_INVALIDARG); // This object only exposes a "default" interface. if(!IsEqualIID(riid, IID_NULL)) return ResultFromScode(DISP_E_UNKNOWNINTERFACE); // It simplifies the following code if the caller // ignores the return value. if(puArgErr == NULL) puArgErr = &uArgErr; if(pvarResult == NULL) pvarResult = &varResultDummy; VariantInit(&varg0); // Assume the return type is void, unless otherwise is found. VariantInit(pvarResult); switch(dispidMember){ case IDMEMBER_CPOINT_GETX: V_VT(pvarResult) = VT_I2; V_I2(pvarResult) = GetX(); break; case IDMEMBER_CPOINT_SETX: HRESULT = DispGetParam(pdispparams, 0, VT_I2, &varg0, puArgErr); if(HRESULT != NOERROR) return hresult; SetX(V_I2(&varg0)); break; case IDMEMBER_CPOINT_GETY: V_VT(pvarResult) = VT_I2; V_I2(pvarResult) = GetY(); break; case IDMEMBER_CPOINT_SETY: HRESULT = DispGetParam(pdispparams, 0, VT_I2, &varg0, puArgErr); if(HRESULT != NOERROR) return hresult; SetY(V_I2(&varg0)); break; default: return ResultFromScode(DISP_E_MEMBERNOTFOUND); } return NOERROR; }
Requirements
Runs on | Versions | Defined in | Include | Link to |
---|---|---|---|---|
Windows CE OS | 2.0 and later | Oleauto.h |
Note This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.