1

我在我的类中定义了以下CComPtr对象和方法：

private:

    CComPtr<IRawPdu>& getRawPdu();
    // Returns the RawPdu interface pointer from the mRawPdu data member.
    // mRawPdu is initialized, if necessary.

    CComPtr<IRawPdu> mRawPdu;
    // Initialized to 0 in the ctor.  Uses lazy evaluation via getRawPdu().

在我的类的构造函数中，我mRawPdu通过初始化列表初始化为 0。如果尚未初始化，则该getRawPdu()方法使用惰性评估。mRawPdu

编译代码时，出现以下错误：

Compiling...
topport.cpp
C:\Program Files\Microsoft Visual Studio 8\VC\atlmfc\include\atlcomcli.h(295) : error C2664: 'ATL::AtlComPtrAssign' : cannot convert parameter 2 from 'const ATL::CComPtr<T>' to 'IUnknown *'
        with
        [
            T=IRawPdu
        ]
        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
        C:\Program Files\Microsoft Visual Studio 8\VC\atlmfc\include\atlcomcli.h(292) : while compiling class template member function 'IRawPdu *ATL::CComPtr<T>::operator =(const ATL::CComPtr<T> &) throw()'
        with
        [
            T=IRawPdu
        ]
        sessionutilities.h(186) : see reference to class template instantiation 'ATL::CComPtr<T>' being compiled
        with
        [
            T=IRawPdu
        ]
topglobals.cpp
C:\Program Files\Microsoft Visual Studio 8\VC\atlmfc\include\atlcomcli.h(295) : error C2664: 'ATL::AtlComPtrAssign' : cannot convert parameter 2 from 'const ATL::CComPtr<T>' to 'IUnknown *'
        with
        [
            T=IRawPdu
        ]
        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
        C:\Program Files\Microsoft Visual Studio 8\VC\atlmfc\include\atlcomcli.h(292) : while compiling class template member function 'IRawPdu *ATL::CComPtr<T>::operator =(const ATL::CComPtr<T> &) throw()'
        with
        [
            T=IRawPdu
        ]
        sessionutilities.h(186) : see reference to class template instantiation 'ATL::CComPtr<T>' being compiled
        with
        [
            T=IRawPdu
        ]

关于可能导致这种情况的任何建议？

4

2 回答 2

2

根据编译器给出的错误，它似乎无法推断出 IRawPdu 和 IUnknown 之间的转换。

它实际上是从 IUnknown 继承的吗？如果是这样，则可能是包含订购问题。您能否更深入地了解 IRawPdu 的层次结构

于 2009-07-01T02:58:26.790 回答
0

不要传递 CComPtr<>，因为没有必要，只需将指针返回到接口。例如：

  IRawPdu* getRawPdu() { return mRawPdu; }   // Does not add to the reference count

  HRESULT get_RawPdu(IRawPdu** ppPdu)   // Returns RawPdu, but add ref's it.
  {
     return mRawPdu.CopyTo(ppPdu);
  }

  CComPtr<IRawPdu> mRawPdu;
  // Initialized to 0 in the ctor.  Uses lazy evaluation via getRawPdu().

因此，当需要使用它时：

  IRawPdu* pTempRawPdu  = class->getRawPdu();
  // use pTempRawPdu in a temporary manner (since it's not add reffed)

但是，更好的是：

  CComPtr<IRawPdu> spRawPdu = class->getRawPdu();
  // the ctor of the local CComPtr<> calls AddRef() (and automagically Release's when done)
于 2009-07-01T03:18:21.710 回答