Question

Why won’t my simple c++ code compile? get undeclared identifier errors.

I can’t see the problem

Thanks a lot

int _tmain(int argc, _TCHAR* argv[])
{
    StateMachine<States,Triggers> sm;

    return 0;
}

enum States
{
    New,
    Complete
};

enum Triggers
{
    CreateNew,
    MoveToComplete
};

template <class TState, class TTrigger> class StateMachine
{
public:
    StateMachine();

};

Answer 1

You have to forward-declare the StateMachine class, otherwise the compiler does not now how to handle that identifier as it hasn’t been told to him what it actually is, yet, or at least, that it exists.

template<class TState, class TTrigger> class StateMachine;

int _tmain(int argc, _TCHAR* argv[])
{
    StateMachine<States,Triggers> sm;

    return 0;
}

// ...

template <class TState, class TTrigger> class StateMachine
{
public:
    StateMachine();

};