Callback.h

#ifndef CALLBACK_
#define CALLBACK_

template <typename Ret, typename Param0>
class Callback
{
  public:
    virtual Ret invoke(Param0 param0) = 0;
};



template <typename Ret, typename Param0>
class StaticFunctionCallback : public Callback<Ret, Param0>
{
  private:
    Ret (*func_)(Param0);
  
  public:
    StaticFunctionCallback(Ret (*func)(Param0))
      : func_(func)
    {}
    
    virtual Ret invoke(Param0 param0)
    {
      return (*func_)(param0);
    }
};



template <typename Ret, typename Param0, typename T, typename Method>
class MethodCallback : public Callback<Ret, Param0>
{
  private:
    void *object_;
    Method method_;
  
  public:
    MethodCallback(void *object, Method method)
      : object_(object)
      , method_(method)
    {}
    
    virtual Ret invoke(Param0 param0)
    {
      T *obj = static_cast<T *>(object_);
      return (obj->*method_)(param0);
    }
};



template <typename Ret, typename Param0>
class Delegate
{
  private:
    Callback<Ret, Param0> *callback_;
    
  public:
    Delegate(Ret (*func)(Param0))
      :callback_(new StaticFunctionCallback<Ret, Param0>(func))
    {}
    
    template <typename T, typename Method>
    Delegate(T *object, Method method)
      :callback_(new MethodCallback<Ret, Param0, T, Method>(object, method))
    {}
    
    ~Delegate(void) { delete callback_; }
    
    Ret operator()(Param0 param0)
    {
      return callback_->invoke(param0);
    }
};
#endif