Converts a variant from one type to another, using a LCID.
HRESULT VariantChangeTypeEx(
VARIANTARG *pvargDest,
VARIANTARG *pvarSrc,
LCID lcid,
unsigned short wFlags,
VARTYPE vt
);
- pvargDest
Pointer to the VARIANTARG to receive the coerced type. If this is the same as pvarSrc, the variant will be converted in place.
- pvarSrc
Pointer to the source VARIANTARG to be coerced.
- lcid
The LCID for the variant to coerce. The LCID is useful when the type of the source or destination VARIANTARG is VT_BSTR, VT_DISPATCH, or VT_DATE.
- wFlags
Flags that control the coercion. Acceptable values are:
VARIANT_NOVALUEPROP. Prevents the function from attempting to coerce an object to a fundamental type by getting the Value property. Applications should set this flag only if necessary, because it makes their behavior inconsistent with other applications.
VARIANT_ALPHABOOL. Converts a VT_BOOL value to a string containing either "True" or "False".
VARIANT_NOUSEROVERRIDE. For conversions to or from VT_BSTR, passes LOCALE_NOUSEROVERRIDE to the core coercion routines.
VARIANT_LOCALBOOL. For conversions from VT_BOOL to VT_BSTR and back, uses the language specified by the locale in use on the local computer.
- vt
The type to coerce to. If the return code is S_OK, the vt field of the *pvargDest is guaranteed to be equal to this value.
The return value obtained from the returned HRESULT is one of the following.
Value | Meaning |
|---|
S_OK | Success. |
DISP_E_BADVARTYPE | The variant type vt is not a valid type of variant. |
DISP_E_OVERFLOW | The data pointed to by pvarSrc does not fit in the destination type. |
DISP_E_TYPEMISMATCH | The argument could not be coerced to the specified type. |
E_INVALIDARG | One of the arguments is invalid. |
E_OUTOFMEMORY | Memory could not be allocated for the conversion. |
The VariantChangeTypeEx function handles coercions between the fundamental types (including numeric-to-string and string-to-numeric coercions). A variant that has VT_BYREF set is coerced to a value by obtaining the referenced value. An object is coerced to a value by invoking the object's Value property (DISPID_VALUE).
Typically, the implementor of IDispatch::Invoke determines which member is being accessed, and then calls VariantChangeType to get the value of one or more arguments. For example, if the IDispatch call specifies a SetTitle member that takes one string argument, the implementor would call VariantChangeTypeEx to attempt to coerce the argument to VT_BSTR.
If VariantChangeTypeEx does not return an error, the argument could then be obtained directly from the bstrVal field of the VARIANTARG. If VariantChangeTypeEx returns DISP_E_TYPEMISMATCH, the implementor would set *puArgErr to 0 (indicating the argument in error) and return DISP_E_TYPEMISMATCH from IDispatch::Invoke.
Arrays of one type cannot be converted to arrays of another type with this function.
.gif) Note: |
|---|
The type of a VARIANTARG should not be changed in the rgvarg array in place. |
Concepts
Reference