您可以使用该函数构造这样的VariantChangeTypeEx
函数。
uses
VarUtils,
Variants;
function TryVarAsType( AVariant : OleVariant; const AVarType: TVarType ) :Boolean;
var
SourceType: TVarType;
begin
SourceType:=TVarData(AVariant).VType;
//the types are ole compatible
if (AVarType and varTypeMask < varInt64) and (SourceType and varTypeMask < varInt64) then
Result:=
(SourceType=AVarType) or
(VariantChangeTypeEx(TVarData(AVariant), TVarData(AVariant), VAR_LOCALE_USER_DEFAULT, 0, AVarType)=VAR_OK)
else
Result:=False; //Here you must process the variant pascal types like varString
end;
并像这样使用
TryVarAsType('1',varInteger);
TryVarAsType('s',varInteger)
这仅适用于与 ole 兼容的 Variant 类型
varEmpty = $0000; { vt_empty 0 }
varNull = $0001; { vt_null 1 }
varSmallint = $0002; { vt_i2 2 }
varInteger = $0003; { vt_i4 3 }
varSingle = $0004; { vt_r4 4 }
varDouble = $0005; { vt_r8 5 }
varCurrency = $0006; { vt_cy 6 }
varDate = $0007; { vt_date 7 }
varOleStr = $0008; { vt_bstr 8 }
varDispatch = $0009; { vt_dispatch 9 }
varError = $000A; { vt_error 10 }
varBoolean = $000B; { vt_bool 11 }
varVariant = $000C; { vt_variant 12 }
varUnknown = $000D; { vt_unknown 13 }
varShortInt = $0010; { vt_i1 16 }
varByte = $0011; { vt_ui1 17 }
varWord = $0012; { vt_ui2 18 }
varLongWord = $0013; { vt_ui4 19 }
varInt64 = $0014; { vt_i8 20 }
对于其他类型(pascal 变体)varString
,varAny
您必须检查源和目标TVarType
并编写自己的测试用例。
更新
正如@David 指出的那样,语言环境设置可以为相同的值产生不同的结果,因此您必须将此答案视为构建您自己的函数的初始步骤或提示,并且您必须了解在提议的函数中引起的语言环境设置问题。