Essential COM

IUnknown

DuplicatePointer DestroyPointer , AddRef Release IUnknown , , . , . AddRef/Release , , .

(Component Object Model Specification) . - C++. :

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    void GetObject([out] IUnknown **ppUnk);

    , :

    void UseObject([in] IUnknown *pUnk);

    , . , , :

    void GetAndUse(/* [out] */ IUnknown ** ppUnkOut) { IUnknown *pUnk1 = 0, *pUnk2 = 0; *ppUnkOut =0; // R3 // get pointers to one (or two) objects // ( ) GetObject(&pUnk1); //A2 GetObject(&pUnk2); //A1 // set pUnk2 to point to first object // pUnk2, if (pUnk2) pUnk2->Release(): //R1 if (pUnk2 = pUnk1) pUnk2->AddRef(): //A1 // pass pUnk2 to some other function // pUnk2 - UseObject(pUnk2); //S1 // return pUnk2 to caller using ppUnkOut parameter // pUnk2 , // ppUnkOut if (*ppUnkOut = pUnk2) (*ppUnkOut)->AddRef(); // A2 // falling out of scope so clean up // if (pUnk1) pUnkl->Release(); //R2 if (pUnk2) pUnk2->Release(); //R2 }

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    inline void SafeRelease(IUnknown * &rpUnk) { if (rpUnk) { rpUnk->Release(); rpUnk = 0; // rpUnk passed by reference // rpUnk, } }

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