CA_VariantConvertToType
HRESULT CA_VariantConvertToType (VARIANT *variant, unsigned int desiredType, void *convertedValue);
Purpose
Converts a value in a variant to a variable with a data type you specify. This can help you when you are uncertain about the data type a variant stores and when you need to work with a particular data type.
CA_VariantConvertToType converts all the fundamental types, such as numeric, string, DATE, CURRENCY, and so on. It converts from a pointer to a value by dereferencing the pointer. It cannot convert to a pointer type, and it cannot convert to or from array types unless the desiredType is exactly the same as the type in the variant.
Upon success, CA_VariantConvertToType frees the contents of the variant parameter, marks it as empty, and sets the type to VT_EMPTY.
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Note If you convert to an array type, the function returns a safe array, not a C-style array. |
Parameters
| Input | ||||||||||||||||||
| Name | Type | Description | ||||||||||||||||
| desiredType | unsigned int | Type to convert the variant value to. desiredType can be any of the fundamental data types for variants, safe arrays, and properties except CAVT_EMPTY or CAVT_NULL. You also can use the CAVT_ARRAY modifier with any of the types. If you do, the type you specify must match exactly the type in the variant, and the function returns a safe array, not a C-style array. If the type of the converted value is char*, CAObjHandle, BSTR, LPDISPATCH, LPUNKNOWN, or an array of any type, you must call the appropriate function to free the convertedValue when you no longer need it. |
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| Output | ||||||||||||||||||
| Name | Type | Description | ||||||||||||||||
| variant | VARIANT | Variant that contains the value to convert. On success, CA_VariantConvertToType frees the variant contents and marks the variant as empty. |
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| convertedValue | void * | The converted value. Pass the address of a variable large enough to hold the converted value. If the type of the converted value is char*, CAObjHandle, BSTR, LPDISPATCH, LPUNKNOWN, or an array of any type, you must call the appropriate function to free convertedValue when it is no longer needed.
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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