VARIANT型別的用法

2021-09-05 16:07:56 字數 1722 閱讀 8931

variant的結構可以參考標頭檔案vc98\include\oaidl.h中關於結構體tagvariant的定義。

對於variant變數的賦值:首先給vt成員賦值,指明資料型別,再對聯合結構中相同資料型別的變數賦值,舉個例子:

variant va;

int a=2001;

va.vt=vt_i4;///指明整型資料

va.lval=a; ///賦值

對於不馬上賦值的variant,最好先用void variantinit(variantarg far* pvarg);進行初始化,其本質是將vt設定為vt_empty,下表我們列舉vt與常用資料的對應關係:

unsigned char bval; vt_ui1

short ival; vt_i2

long lval; vt_i4

float fltval; vt_r4

double dblval; vt_r8

variant_bool boolval; vt_bool

scode scode; vt_error

cy cyval; vt_cy

date date; vt_date

bstr bstrval; vt_bstr

iunknown far* punkval; vt_unknown

idispatch far* pdispval; vt_dispatch

safearray far* parray; vt_array|*

unsigned char far* pbval; vt_byref|vt_ui1

short far* pival; vt_byref|vt_i2

long far* plval; vt_byref|vt_i4

float far* pfltval; vt_byref|vt_r4

double far* pdblval; vt_byref|vt_r8

variant_bool far* pboolval; vt_byref|vt_bool

scode far* pscode; vt_byref|vt_error

cy far* pcyval; vt_byref|vt_cy

date far* pdate; vt_byref|vt_date

bstr far* pbstrval; vt_byref|vt_bstr

iunknown far* far* ppunkval; vt_byref|vt_unknown

idispatch far* far* ppdispval; vt_byref|vt_dispatch

safearray far* far* pparray; vt_array|*

variant far* pvarval; vt_byref|vt_variant

void far* byref; vt_byref

_variant_t是variant的封裝類,其賦值可以使用強制型別轉換,其建構函式會自動處理這些資料型別。

例如:

long l=222;

ing i=100;

_variant_t lval(l);

lval = (long)i;

colevariant v3 = "字串", v4 = (long)1999;

cstring str =(bstr)v3.pbstrval;

long i = v4.lval;

VARIANT 資料型別

variant 資料型別在檔案oaidl.idl中定義如下 vc中資料型別,對應類為 variant t struct tagvariant variant name 4 vt record variant name 3 variant name 2 decimal decval variant n...

VARIANT 資料型別

variant 資料型別在檔案oaidl.idl中定義如下 vc中資料型別,對應類為 variant t struct tagvariant variant name 4 vt record variant name 3 variant name 2 decimal decval variant n...

VARIANT 資料型別

variant 資料型別在檔案oaidl.idl中定義如下 vc中資料型別,對應類為 variant t struct tagvariant variant name 4 vt record variant name 3 variant name 2 decimal decval variant n...