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Desk four. four IUnknown strategy Names approach identify Description CUnknown undefined, which initializes the reference count number for this example of the CUnknown type to one. Returns a pointer to the IUnknown interface for the article. Public helper process that casts a CUnknown pointer to an IUnknown pointer. Increments the reference count number for the item. Decrements the object’s reference count number and deletes the item if the reference count number reaches 0. QueryInterface QueryIUnknown AddRef unlock Wow! booklet 96 bankruptcy four Programming Drivers for the UMDF four. 7. 2 IClassFactory Interface The CClassFactory type item implements the IClassFactory interface. The framework invokes tools during this interface to create an example of the motive force callback classification. the driving force callback classification example is the one callback item that the framework creates; the driving force itself creates all different callback gadgets in accordance with calls from the framework. desk four. five summarizes the tools during this interface. four. 7. three motive force CallBack item whilst UMDF will get a pointer to the IClassFactory interface, it calls the CreateInstance process in that interface to create an example of an item. That technique, in flip, calls the CMyDriver::CreateInstance technique, which creates and initializes the driving force callback item. ordinarily, any CreateInstance technique is a manufacturing unit technique that creates an item. desk four. five IClassFactory tools process Description QueryInterface QueryIClassFactory Returns a pointer to the asked interface. Public helper approach that casts a CClassFactory pointer to an IClassFactory pointer; primarily just like the IQueryIUnknown strategy within the IUnknown interface. Creates an example of the driving force callback classification and returns a pointer to a asked interface for that classification. keeps a lock count number that exhibits even if the motive force DLL should still stay in reminiscence. CreateInstance LockServer Wow! publication 4. 7 capabilities for COM help ninety seven CMyDriver::CreateInstance is outlined within the resource dossier motive force. cpp and is easy, because the following indicates: HRESULT CMyDriver::CreateInstance( __out PCMyDriver *Driver ) /*++ regimen Description: This static technique is invoked to create and initialize a brand new example of the driving force category. The caller may still organize for the item to be published whilst it really is not in use. Arguments: motive force - a place to shop a referenced pointer to the hot example go back price: S_OK if winning, or mistakes in a different way --*/ { PCMyDriver driving force; HRESULT hr; // // Allocate the callback item // motive force = new CMyDriver(); if (NULL == driving force) { go back E_OUTOFMEMORY; } // // Initialize the callback item // hr = driver->Initialize(); if (SUCCEEDED (hr)) { Wow! booklet 98 bankruptcy four Programming Drivers for the UMDF // // shop a pointer to the recent, initialized item in // the output parameter. // *Driver = motive force; } else { // // unencumber the reference at the motive force item in order that // it is going to delete itself // driver->Release(); } go back hr; } this technique allocates and creates an example of the driving force callback item, after which calls the initialize approach to initialize the thing.