VARIANT and VARIANTARG

This structure is used to describe arguments passed within DISPPARAMS, and VARIANT to specify variant data that cannot be passed by reference. The VARIANT type cannot have the VT_BYREF bit set.

typedef struct tagVARIANT {
 VARTYPE vt;
 unsigned short wReserved1;
 unsigned short wReserved2;
 unsigned short wReserved3;
 union {
 unsigned char bVal;
 short iVal;
 long lVal;
 float fltVal;.
 double dblVal;
 VARIANT_BOOL boolVal;
 SCODE scode;
 CY cyVal;
 DATE date;
 BSTR bstrVal;
 IUnknown FAR* punkVal;
 IDispatch FAR* pdispVal;
 SAFEARRAY FAR* parray;
 unsigned char FAR* pbVal;
 short FAR* piVal;
 long FAR* plVal;
 float FAR* pfltVal;
 double FAR* pdblVal;
 VARIANT_BOOL FAR* pboolVal;
 SCODE FAR* pscode;
 CY FAR* pcyVal;
 DATE FAR* pdate;
 BSTR FAR* pbstrVal;
 IUnknown FAR* FAR* ppunkVal;
 IDispatch FAR* FAR* ppdispVal;
 SAFEARRAY FAR* FAR* pparray;
 VARIANT FAR* pvarVal;
 void FAR* byref;
 };
};
typedef struct FARSTRUCT tagVARIANT VARIANT;
typedef struct FARSTRUCT tagVARIANT VARIANTARG;

Members

vt
wReserved1
wReserved2
wReserved3
bVal
VT_UI1.
iVal
VT_I2.
lVal
VT_I4.
fltVal
VT_R4.
dblVal
VT_R8.
boolVal
VT_BOOL.
scode
VT_ERROR.
cyVal
VT_CY.
date
VT_DATE.
bstrVal
VT_BSTR.
punkVal
VT_UNKNOWN.
pdispVal
VT_DISPATCH.
parray
VT_ARRAY | *.
pbVal
VT_BYREF | VT_UI1.
piVal
VT_BYREF | VT_I2.
plVal
VT_BYREF | VT_I4.
pfltVal
VT_BYREF | VT_R4.
pdblVal
VT_BYREF | VT_R8.
pboolVal
VT_BYREF | VT_BOOL.
pscode
VT_BYREF | VT_ERROR.
pcyVal
VT_BYREF | VT_CY.
pdate
VT_BYREF | VT_DATE.
pbstrVal
VT_BYREF | VT_BSTR.
ppunkVal;
VT_BYREF | VT_UNKNOWN.
ppdispVal;
VT_BYREF | VT_DISPATCH.
pparray;
VT_ARRAY | *.
pvarVal
VT_BYREF | VT_VARIANT.
byref
Generic ByRef

Return Values

To simplify extracting values from VARIANTARGs, Automation provides a set of functions for manipulating this type. Use of these functions is strongly recommended to ensure that applications apply consistent coercion rules.

The vt value governs the interpretation of the union as follows:

VT_EMPTY
No value was specified. If an optional argument to an Automation method is left blank, do not pass a VARIANT of type VT_EMPTY. Instead, pass a VARIANT of type VT_ERROR with a value of DISP_E_PARAMNOTFOUND.
VT_EMPTY | VT_BYREF
Not valid.
VT_UI1
An unsigned 1-byte character is stored in bVal.
VT_UI1 | VT_BYREF
A reference to an unsigned 1-byte character was passed. A pointer to the value is in pbVal.
VT_I2
A 2-byte integer value is stored in iVal.
VT_I2 | VT_BYREF
A reference to a 2-byte integer was passed. A pointer to the value is in piVal.
VT_I4
A 4-byte integer value is stored in lVal.
VT_I4 | VT_BYREF
A reference to a 4-byte integer was passed. A pointer to the value is in plVal.
VT_R4
An IEEE 4-byte real value is stored in fltVal.
VT_R4 | VT_BYREF
A reference to an IEEE 4-byte real value was passed. A pointer to the value is in pfltVal.
VT_R8
An 8-byte IEEE real value is stored in dblVal.
VT_R8 | VT_BYREF
A reference to an 8-byte IEEE real value was passed. A pointer to its value is in pdblVal.
VT_CY
A currency value was specified. A currency number is stored as an 8-byte, two complement integer, scaled by 10,000 to give a fixed-point number with 15 digits to the left of the decimal point and 4 digits to the right. The value is in cyVal.
VT_CY | VT_BYREF
A reference to a currency value was passed. A pointer to the value is in pcyVal.
VT_BSTR
A string was passed; it is stored in bstrVal. This pointer must be obtained and freed by the BSTR functions.
VT_BSTR | VT_BYREF
A reference to a string was passed. A BSTR* that points to a BSTR is in pbstrVal. The referenced pointer must be obtained or freed by the BSTR functions.
VT_NULL
A propagating null value was specified. (This should not be confused with the null pointer.) The null value is used for tri-state logic, as with SQL.
VT_NULL | VT_BYREF
Not valid.
VT_ERROR
An SCODE was specified. The type of the error is specified in scodee. Generally, operations on error values should raise an exception or propagate the error to the return value, as appropriate.
VT_ERROR | VT_BYREF
A reference to an SCODE was passed. A pointer to the value is in pscode.
VT_BOOL
A Boolean (True/False) value was specified. A value of 0xFFFF (all bits 1) indicates True; a value of 0 (all bits 0) indicates False. No other values are valid.
VT_BOOL | VT_BYREF
A reference to a Boolean value. A pointer to the Boolean value is in pbool.
VT_DATE
A value denoting a date and time was specified. Dates are represented as double-precision numbers, where midnight, January 1, 1900 is 2.0, January 2, 1900 is 3.0, and so on. The value is passed in date.

This is the same numbering system used by most spreadsheet programs, although some specify incorrectly that February 29, 1900 existed, and thus set January 1, 1900 to 1.0.

VT_DATE | VT_BYREF
A reference to a date was passed. A pointer to the value is in pdate.
VT_DISPATCH
A pointer to an object was specified. The pointer is in pdispVal. This object is known only to implement IDispatch. The object can be queried as to whether it supports any other desired interface by calling QueryInterface on the object. Objects that do not implement IDispatch should be passed using VT_UNKNOWN.
VT_DISPATCH | VT_BYREF
A pointer to a pointer to an object was specified. The pointer to the object is stored in the location referred to by ppdispVal.
VT_VARIANT
Invalid. VARIANTARGs must be passed by reference.
VT_VARIANT | VT_BYREF
A pointer to another VARIANTARG is passed in pvarVal. This referenced VARIANTARG will never have the VT_BYREF bit set in vt, so only one level of indirection can ever be present. This value can be used to support languages that allow functions to change the types of variables passed by reference.
VT_UNKNOWN
A pointer to an object that implements the IUnknown interface is passed in punkVal.
VT_UNKNOWN | VT_BYREF
A pointer to the IUnknown interface is passed in ppunkVal. The pointer to the interface is stored in the location referred to by ppunkVal.
VT_ARRAY | <anything>

An array of data type <anything> was passed. (VT_EMPTY and VT_NULL are invalid types to combine with VT_ARRAY.) The pointer in pbyrefVal points to an array descriptor, which describes the dimensions, size, and in-memory location of the array.

Requirements

  Windows CE versions: 2.0 and later  
  Header file: Declared in Oaidl.h
  Platform: H/PC Pro, Palm-size PC, Pocket PC

Show: