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Exporting the Implementation Factories

An implementation collection gathers one or more interface implementations in a DLL. It provides necessary information to the plug-in framework to use them. The collection must export a single function that provides an array. This array maps the UID of each implementation it contains with a pointer to its factory instantiation function (NewL() in our example).

Define a UID for each implementation. This UID maps to the instantiation function of the implementation. Construct an array of UID's for all the implementations in the collection.

        
         
        
        // Define the interface UIDs
const TImplementationProxy ImplementationTable[] = 
    {
    {{0x10009DC3}, CImplementationClassOne::NewL();},
    {{0x10009DC4}, CImplementationClassTwo::NewL();}
    };
    }

The signature of this exported function must be:

        
         
        
        const TImplementationProxy* ImplementationGroupProxy(TInt& aTableCount);

The exported function returns a pointer to an array of TImplementationProxy objects.

Each TImplementationProxy contains a UID and a function pointer. aTableCount should be set to the number of items in the array.

        
         
        
        EXPORT_C const TImplementationProxy* ImplementationGroupProxy(TInt& aTableCount)
    {
    aTableCount = sizeof(ImplementationTable) / sizeof(TImplementationProxy);

    return ImplementationTable;
    }

Parent topic: Plug-in Writer's Tutorial