VARIANT与其它类型的相互转换.doc

VARIANT与其它类型的相互转换(原创)

我想刚做串口通信的同志们可能都遇到过VARIANT类型变量的问题吧。这个问题前两天使我很苦恼，不知道是什么类型，更不知道如何相互转换，今天终于找到了一些信息。我把这些转换的例子贴出来，与大家共享。

//DeclarevariableVARIANTvtTest;CStringstrTest;CStringstrOut;intnTest;
//CString->VARIANT->CStringstrTest="陈水扁";vtTest.vt=VT_BSTR;vtTest.bstrVal=strTest.AllocSysString();strOut=vtTest.bstrVal;MessageBox(strOut);
//int->VARIANT->intvtTest.vt=VT_R8;vtTest.iVal=20;nTest=vtTest.iVal;strOut.Format("%d",nTest);MessageBox(strOut);

至于其它类型应该也是用类似的用法吧（哈哈，其它的我也没试）。下面是MSDN中关于这个变量的定义：

VARIANTandVARIANTARG
ThisstructureisusedtodescribeargumentspassedwithinDISPPARAMS,andVARIANTtospecifyvariantdatathatcannotbepassedbyreference.TheVARIANTtypecannothavetheVT_BYREFbitset.
typedefstructtagVARIANT{
VARTYPEvt;
unsignedshortwReserved1;
unsignedshortwReserved2;
unsignedshortwReserved3;
union{
unsignedcharbVal;
shortiVal;
longlVal;
floatfltVal;.
doubledblVal;
VARIANT_BOOLboolVal;
SCODEscode;
CYcyVal;
DATEdate;
BSTRbstrVal;
IUnknownFAR*punkVal;
IDispatchFAR*pdispVal;
SAFEARRAYFAR*parray;
unsignedcharFAR*pbVal;
shortFAR*piVal;
longFAR*plVal;
floatFAR*pfltVal;
doubleFAR*pdblVal;
VARIANT_BOOLFAR*pboolVal;
SCODEFAR*pscode;
CYFAR*pcyVal;
DATEFAR*pdate;
BSTRFAR*pbstrVal;
IUnknownFAR*FAR*ppunkVal;
IDispatchFAR*FAR*ppdispVal;
SAFEARRAYFAR*FAR*pparray;
VARIANTFAR*pvarVal;
voidFAR*byref;
};
};
typedefstructFARSTRUCTtagVARIANTVARIANT;
typedefstructFARSTRUCTtagVARIANTVARIANTARG;
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
Gener