FunctionRef.h

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#pragma once
 
// Declared only so it can be partially specialized
template <class Signature>
class cFunctionRef;
 
template <class Ret, class... Args>
class cFunctionRef<Ret(Args...)>
{
public:
    template <class FunctionObject,
        typename std::enable_if<  // Don't disable the default copy constructor
            !std::is_same<typename std::decay<FunctionObject>::type, cFunctionRef>::value,
        int>::type = 0
    >
    cFunctionRef(FunctionObject && a_FunctionObject)
    {
        // Store an opaque reference to the object.
        m_CallableData = &a_FunctionObject;
 
        // Along with a function that knows how to call the object.
        m_CallFunction = &ObjectFunctionCaller<FunctionObject>;
    }
 
    Ret operator () (Args... a_Args)
    {
        return m_CallFunction(m_CallableData, std::forward<Args>(a_Args)...);
    }
 
private:
 
    template <class ObjectType>
    static Ret ObjectFunctionCaller(void * a_Callable, Args...  a_Args)
    {
        // Convert opaque reference to the concrete type.
        using ObjectPtr = typename std::add_pointer<ObjectType>::type;
        auto & Object = *static_cast<ObjectPtr>(a_Callable);
 
        // Forward the call down to the object.
        return Object(std::forward<Args>(a_Args)...);
    }
 
    using cCallFunction = Ret(*)(void *, Args...);
 
    void * m_CallableData;
 
    cCallFunction m_CallFunction;
};