[英]How do you access to SAFE ARRAY in a VARIANT data type returned from a COM object in C++?
我正在使用COM对象。 我调用一个COM对象的函数,此函数返回包含我的设备列表的安全数组的VARIANT数据类型。 如何使用此变量来访问我的设备的SAFEARRY。
VARIANT namList;
SAFEARRAY* myequip;
namList=str->GetNames();
为了在这样的VARIANT中使用SAFEARRAY,您需要进行大量的验证和错误检查。 这是您需要遵循的粗略模式。 由于我对您使用的COM API做出了一些假设,因此请仔细阅读注释。
// verify that it's an array
if (V_ISARRAY(&namList))
{
// get safe array
LPSAFEARRAY pSafeArray = V_ARRAY(&namList);
// determine the type of item in the array
VARTYPE itemType;
if (SUCCEEDED(SafeArrayGetVartype(pSafeArray, &itemType)))
{
// verify it's the type you expect
// (The API you're using probably returns a safearray of VARIANTs,
// so I'll use VT_VARIANT here. You should double-check this.)
if (itemType == VT_VARIANT)
{
// verify that it's a one-dimensional array
// (The API you're using probably returns a one-dimensional array.)
if (SafeArrayGetDim(pSafeArray) == 1)
{
// determine the upper and lower bounds of the first dimension
LONG lBound;
LONG uBound;
if (SUCCEEDED(SafeArrayGetLBound(pSafeArray, 1, &lBound)) && SUCCEEDED(SafeArrayGetUBound(pSafeArray, 1, &uBound)))
{
// determine the number of items in the array
LONG itemCount = uBound - lBound + 1;
// begin accessing data
LPVOID pData;
if (SUCCEEDED(SafeArrayAccessData(pSafeArray, &pData)))
{
// here you can cast pData to an array (pointer) of the type you expect
// (The API you're using probably returns a safearray of VARIANTs,
// so I'll use VARIANT here. You should double-check this.)
VARIANT* pItems = (VARIANT*)pData;
// use the data here.
// end accessing data
SafeArrayUnaccessData(pSafeArray);
}
}
}
}
}
}
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