templates may not be ‘virtual’

Question

Given the code below, the compiler is showing a message pointing that error: templates may not be ‘virtual’. Does anyone have a suggestion on how to solve the bug?<

Answer 1

You can use what we call in Symbian as "template design pattern". Here is sample code to give you an idea:

class Base {
public:
        virtual int DoSomething() = 0;
protected:
        Base();
};

class IntermediateBase : public Base {
protected:
        IntermediateBase(void* aSomeParam, void* aArg)
        : iSomeParam(aSomeParam)
        , iArgs(aArg) 
        {}

        virtual int DoSomething() = 0;
protected:
        void* iSomeParam;
        void* iArgs;
};

template 
class ConcreteClass : public IntermediateBase {
        typedef int (TYPE::*MemberFuncPtr)(const INPUT&);
public:
        ConcreteClass(TYPE& aCommandType, 
                      INPUT& aArgumentsToCommand,
                      MemberFuncPtr aMFP)
        : IntermediateBase(static_cast(&aCommandType),
                           static_cast(&aArgumentsToCommand) )
        , iMFP(aMFP)
        {}

        virtual int DoSomething()  // VIRTUAL AND INLINE Note - dont make it 
                                   // virtual and inline in production if 
                                   // possible to avoid out-of-line copy   
        {
            return static_cast(iSomeParam)->*ConcreteClass::iMFP)
                           (*(static_cast(iArgs));
        }
private:
        MemberFuncPtr iMFP;
};