_bstr_t在VC中是为了兼容BSTR类型而增加
也就是为了实现LPCSTR和BSTR转换
它需要头文件#
<comdef.h> _bstr_t 是BSTR
包装类 转换思路方法
LPSTR strDemo="Test";
_bstr_t bstr(strDemo);
建议加上try
catch用于catch(_com_error &e) The following pseudocode shows the typical use of CComBSTR:
HRESULT CMyObject::MyMethod(IOtherObject* pSomething)
{
CComBSTR bstrText(L"Hello");
bstrText
" again"; // LPCSTR conversion bstrText.ToUpper
; pSomething->Display(bstrText); // [in] parameter
MessageBoxW(0, bstrText, L"Test", MB_OK); // Assumes Windows NT
}
As you can see, CComBSTR sign
icantly simplies the use of BSTRs. Four uses of CComBSTR, however, require special care: Freeing the BSTR explicitly
Using CComBSTR as an [out] parameter
Using a CComBSTR automatic variable in right-side assignments
Using a CComBSTR member variable in right-side assignments
当在BSTR*所在
位置作为
个[out]参数传递CComBSTR时你必须先
Empty释放
内容就象下面这样:HRESULT CMyObject::MyMethod2(ISomething* p, /*[out]*/ BSTR* pbstr) {
CComBSTR bstrText;
bstrText = L"Some assignment"; // BSTR is allocated.
bstrText.Empty
; // Must call empty before pSomething->GetText(&bstrText); // using as an [out] parameter.
(bstrText != L"Schaller") bstrText
"Hello"; // Convert from LPCSTR. }
在重写BSTR内容的前思路方法COM 为[out] 参数规则是并不sysfree,这讲出现泄漏
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