VariantChangeType function

Converts a variant from one type to another.

Syntax

HRESULT VariantChangeType(
  _Out_       VARIANTARG *pvargDest,
  _In_  const VARIANTARG *pvarSrc,
  _In_        USHORT     wFlags,
  _In_        VARTYPE    vt
);

Parameters

pvargDest [out]

The destination variant. If this is the same as pvarSrc, the variant will be converted in place.

pvarSrc [in]

The variant to convert.

wFlags [in]

Flags.

Value	Meaning
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 [in]

The type to convert to. If the return code is S_OK, the vt field of the *pvargDest is guaranteed to be equal to this value.

Return value

This function can return one of these values.

Remarks

The VariantChangeType function handles coercions between the fundamental types (including numeric-to-string and string-to-numeric coercions). The pvarSrc argument is changed during the conversion process. For example, if the source variant is of type VT_BOOL and the destination is of type VT_UINT, the pvarSrc argument is first converted to VT_I2 and then the conversion proceeds. 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 VariantChangeType to attempt to coerce the argument to VT_BSTR. If VariantChangeType does not return an error, the argument could then be obtained directly from the bstrVal field of the VARIANTARG. If VariantChangeType returns DISP_E_TYPEMISMATCH, the implementor would set *puArgErr to 0 (indicating the argument in error) and return DISP_E_TYPEMISMATCH from Invoke.

Arrays of one type cannot be converted to arrays of another type with this function.

Requirements

See also

VariantChangeTypeEx

Variant Manipulation Functions