转：MFC之COleVariant

COleVariant 本质上是一个枚举，用同一种类型来表达不同的子类型。如同boost中的variant。

例子

[cpp] view plaincopy

COleVariant var(3.6f);
float v = var.fltVal;
CString str("testCOleVariant");
COleVariant var2(str);
CString cpStr(var2.bstrVal);

例子

[cpp] view plaincopy

CString CMFCPropertyGridProperty::m_strFormatChar = _T("%c");
CString CMFCPropertyGridProperty::m_strFormatShort = _T("%d");
CString CMFCPropertyGridProperty::m_strFormatLong = _T("%ld");
CString CMFCPropertyGridProperty::m_strFormatUShort = _T("%u");
CString CMFCPropertyGridProperty::m_strFormatULong = _T("%u");
CString CMFCPropertyGridProperty::m_strFormatFloat = _T("%f");
CString CMFCPropertyGridProperty::m_strFormatDouble = _T("%lf");
CString CMFCPropertyGridProperty::FormatProperty()
{
ASSERT_VALID(this);
ASSERT_VALID(m_pWndList);
COleVariant& var = m_varValue;
CString strVal;
.............
switch (var.vt)
{
case VT_BSTR:
strVal = var.bstrVal;
break;
case VT_I2:
strVal.Format(m_strFormatShort, (short)var.iVal);
break;
case VT_I4:
case VT_INT:
strVal.Format(m_strFormatLong, (long)var.lVal);
break;
case VT_UI1:
if ((BYTE)var.bVal != 0)
{
strVal.Format(m_strFormatChar, (TCHAR)(BYTE)var.bVal);
}
break;
case VT_UI2:
strVal.Format( m_strFormatUShort, var.uiVal);
break;
case VT_UINT:
case VT_UI4:
strVal.Format(m_strFormatULong, var.ulVal);
break;
case VT_R4:
strVal.Format(m_strFormatFloat, (float)var.fltVal);
break;
case VT_R8:
strVal.Format(m_strFormatDouble, (double)var.dblVal);
break;
case VT_BOOL:
strVal = var.boolVal == VARIANT_TRUE ? m_pWndList->m_strTrue : m_pWndList->m_strFalse;
break;
default:
// Unsupported type
strVal = _T("*** error ***");
}
return strVal;
}

COleVariant框架内容

[cpp] view plaincopy

class COleVariant : public tagVARIANT
{
COleVariant(LPCTSTR lpszSrc);
COleVariant(LPCTSTR lpszSrc, VARTYPE vtSrc); // used to set to ANSI string
COleVariant(CString& strSrc);
COleVariant(BYTE nSrc);
COleVariant(short nSrc, VARTYPE vtSrc = VT_I2);
COleVariant(long lSrc, VARTYPE vtSrc = VT_I4);
COleVariant(const COleCurrency& curSrc);
COleVariant(float fltSrc);
COleVariant(double dblSrc);
COleVariant(const COleDateTime& timeSrc);
....................................
const COleVariant& operator=(float fltSrc);
const COleVariant& operator=(double dblSrc);
const COleVariant& operator=(const COleDateTime& dateSrc);
const COleVariant& operator=(const CByteArray& arrSrc);
const COleVariant& operator=(const CLongBinary& lbSrc);
};
void Clear();
void ChangeType(VARTYPE vartype, LPVARIANT pSrc = NULL);
void Attach(VARIANT& varSrc);
VARIANT Detach();
void GetByteArrayFromVariantArray(CByteArray& bytes);
void SetString(LPCTSTR lpszSrc, VARTYPE vtSrc); // used to set ANSI string
operator LPVARIANT();
operator LPCVARIANT() const
/
struct tagVARIANT
{ union
{
struct __tagVARIANT
{
VARTYPE vt;
.......................
union
{
LONGLONG llVal;
LONG lVal;
BYTE bVal;
SHORT iVal;
FLOAT fltVal;
DOUBLE dblVal;
...........
DATE date;
BSTR bstrVal;
IUnknown *punkVal;
IDispatch *pdispVal;
..............
}
COleVariant::COleVariant(float fltSrc)
{ vt = VT_R4; fltVal = fltSrc; }
_AFXDISP_INLINE COleVariant::COleVariant(CString& strSrc)
{ vt = VT_EMPTY; *this = strSrc; }
const COleVariant& COleVariant::operator=(const CString& strSrc)
{
// Free up previous VARIANT
Clear();
vt = VT_BSTR;
bstrVal = strSrc.AllocSysString();
return *this;
}
typedef unsigned short VARTYPE;
/*
* VARENUM usage key,
*
* * [V] - may appear in a VARIANT
* * [T] - may appear in a TYPEDESC
* * [P] - may appear in an OLE property set
* * [S] - may appear in a Safe Array
*
*
* VT_EMPTY [V] [P] nothing
* VT_NULL [V] [P] SQL style Null
* VT_I2 [V][T][P][S] 2 byte signed int
* VT_I4 [V][T][P][S] 4 byte signed int
* VT_R4 [V][T][P][S] 4 byte real
* VT_R8 [V][T][P][S] 8 byte real
* VT_CY [V][T][P][S] currency
* VT_DATE [V][T][P][S] date
* VT_BSTR [V][T][P][S] OLE Automation string
* VT_DISPATCH [V][T] [S] IDispatch *
* VT_ERROR [V][T][P][S] SCODE
* VT_BOOL [V][T][P][S] True=-1, False=0
* VT_VARIANT [V][T][P][S] VARIANT *
* VT_UNKNOWN [V][T] [S] IUnknown *
* VT_DECIMAL [V][T] [S] 16 byte fixed point
.......................................
enum VARENUM
{ VT_EMPTY = 0,
VT_NULL = 1,
VT_I2 = 2,
VT_I4 = 3,
VT_R4 = 4,
VT_R8 = 5,
VT_CY = 6,
VT_DATE = 7,
VT_BSTR = 8,
.........................................
} ;

转载于:https://www.cnblogs.com/yfz0/p/5862089.html

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