CA_VariantGetIUnknown
HRESULT CA_VariantGetIUnknown (VARIANT *variant, LPUNKNOWN *value);
Purpose
Copies the value in a variant into a LPUNKNOWN variable. An LPUNKNOWN value is a pointer to an unknown interface.
On success, CA_VariantGetIUnknown marks the variant parameter as empty.
CA_VariantGetIUnknown returns an error if the variant does not contain an LPUNKNOWN value.
Parameters
| Output | ||
| Name | Type | Description |
| variant | VARIANT | Pointer to a variant that contains an LPUNKNOWN value. CA_VariantGetIUnknown marks the variant as empty on success. |
| value | LPUNKNOWN | LPUNKNOWN value that CA_VariantGetIUnknown copies from the variant. When you no longer need the LPUNKNOWN, free it by calling its Release function, as shown in the following example: lpUnknown->lpVtbl->Release(lpUnknown); |
Return Value
| Name | Type | Description |
| status | HRESULT | A value indicating whether an error occurred. Negative error codes indicate function failure. Error codes are defined in CVIversion\include\cviauto.h and <Program Files>\National Instruments\Shared\MSDTRedistributables\SDKHeaderFiles\8.1\winerror.h. The LabWindows/CVI ActiveX Library explicitly returns error codes. Other error codes in winerror.h are generated by ActiveX servers and passed on to you by the LabWindows/CVI ActiveX Library. You can use CA_GetAutomationErrorString to get the description of an error code or CA_DisplayErrorInfo to display the description of the error code. |
Additional Information
Library: ActiveX Library
Include file: cviauto.h
LabWindows/CVI compatibility: LabWindows/CVI 5.0 and later