pIUnknown->QueryInterface(const IID& iid, void** ppv)中第一参数如何理解

Question

COM中，通过pIUnknown->QueryInterface(const IID& iid, void** ppv)来查询，但第一个参数不理解，他不是类ID,是接口ID，但这个const IID& iid是个什么值，是默认的吗？不是默认的如何获取？

Answer 1

就是com组件每一个都有一个id，类似名字的概念，你通过这个名字来查找，从而通过ppv把它的接口返回给你

Answer 2

// Generated .IDL file (by the OLE/COM Object Viewer)
// 
// typelib filename: XCDZIP35.OCX[
  uuid(B26F6243-4C7D-11D1-910E-00600807163F),
  version(2.78),
  helpstring("Xceed Zip ActiveX Control")
]
library XCEEDZIPLib
{
    // TLib :     // TLib : Standard OLE Types : {BEF6E001-A874-101A-8BBA-00AA00300CAB}
    importlib("olepro32.dll");
    // TLib : OLE Automation : {00020430-0000-0000-C000-000000000046}
    importlib("stdole32.tlb");    // Forward declare all types defined in this typelib
    dispinterface _DXceedZip;
    dispinterface _DXceedZipEvents;    [
      uuid(B26F6244-4C7D-11D1-910E-00600807163F),
      helpstring("Dispatch interface for the Xceed Zip Control"),
      hidden
    ]
    dispinterface _DXceedZip {
        properties:
            [id(0x00000001)]
            VARIANT_BOOL Abort;
            [id(0x00000002)]
            short Compression;
  
             ..........
            [id(0xfffffdd8)]
            void AboutBox();
    };    [
      uuid(B26F6245-4C7D-11D1-910E-00600807163F),
      helpstring("Event interface for the Xceed Zip Control")
    ]
    dispinterface _DXceedZipEvents {
        properties:
        methods:
            [id(0x00000001)]
            void Adding(
                            BSTR* FileName, 
                            long Size, 
                            long PSize, 
                            long Processed, 
                            short FileAttr, 
                            BSTR* FTime, 
                            long CRC, 
                            short Ratio, 
                            short Completion, 
                            short Method, 
                            short Encrypted, 
                            short ComLen, 
                            BSTR* Comment);
            [id(0x00000002)]
            void Deleting(BSTR* FileName);
            [id(0x00000003)]
            void Extracting(
                            BSTR* FileName, 
                            long Size, 
                            long PSize, 
                            long Processed, 
                            short FileAttr, 
                            BSTR* FTime, 
                            long CRC, 
                            short Ratio, 
                            short Completion, 
                            short Method, 
                            short Encrypted, 
                            short ComLen, 
                            BSTR* Comment);
            [id(0x00000004)]
            void FileComment(
                            BSTR* FileName, 
                            short* ComLen, 
                            BSTR* Comment);
            [id(0x00000005)]
            void Fixing(BSTR* FileName);
            [id(0x00000006)]
            void Listing(
                            BSTR* FileName, 
                            long Size, 
                            long PSize, 
                            long Processed, 
                            short FileAttr, 
                            BSTR* FTime, 
                            long CRC, 
                            short Ratio, 
                            short Completion, 
                            short Method, 
                            short Encrypted, 
                            short ComLen, 
                            BSTR* Comment);
            
........................
            [id(0x0000000f)]
            void Rename(
                            BSTR* OrigName, 
                            BSTR* NewName);
    };    [
      uuid(B26F6246-4C7D-11D1-910E-00600807163F),
      helpstring("Xceed Zip Control"),
      control
    ]
    coclass XceedZip {
        [default] dispinterface _DXceedZip;
        [default, source] dispinterface _DXceedZipEvents;
    };
};是不是UUID这些呢

Answer 3

帮我看个简单的OCX加载问题,谢谢了
const GUID   MyOcxCLSID = {0xB26F6246,0x4C7D,0x11D1,0x91,0x0E,0x00,0x60,0x08,0x07,0x16,0x3F};  //我的OCX,CLSID
if (CoInitialize(NULL) != S_OK) {
printf("Initialize COM library failed!\n");
return 1L;
} hResult = CoCreateInstance(MyOcxCLSID, NULL,CLSCTX_INPROC_SERVER, IID_IUnknown, (void **)&pUnknown);
if (hResult != S_OK) 
{
printf("Create object failed!\n");
return 1L;
}//返回了IID_IUnknown是{00020430-0000-0000-C000-000000000046} //这个IID好象不是我要的
象是系统OLE hResult = pUnknown->QueryInterface(IID_IUnknown, (void **)&ppIface);
if (hResult != S_OK) {
pUnknown->Release();
printf("QueryInterface IDictionary failed!\n");
CoUninitialize();
return 1L;
}//返回的ppIface，通过**查询，也到不了我的OCX那里，我查了我的OCX是加载到10001000上面，而这个指针指向的地址在5FXXXXXX那，不是我的OCX代码
if (pUnknown->Release()!= 0) 
CoUninitialize(); return 1L;

Answer 4

com 本质论系统学习一下。

Answer 5

LS正解，搞本书看看。
这个id叫接口ID，说白了，你想要这个COM组件的什么功能，就传递什么接口ID就可以了。

Answer 6

一个对象可以有多个接口，CLS_ID是对象的ID，IID是接口的ID

Answer 7

就是一个UUID ,一般你需要把它所在定义的.h文件包起来，不包也行，反正UUID不会变，你复制到你的.h文件 里面直接用，也可以的。

Answer 8

一个组件具体实现了哪些接口，作者会在文档里说。没有文档只有一个IUnknown你什么都干不了。