Hands-On Design Patterns with C++

Type erasure in C++

Let's finally see how std::shared_ptr does its magic. We will do it with a simplified example of a smart pointer that focuses specifically on the type erasure aspect. It should not surprise you to learn that this is done with a combination of generic and object-oriented programming:

template <typename T>class smartptr {    struct deleter_base {        virtual void apply(void*) = 0;        virtual ~deleter_base() {}    };    template <typename Deleter>     struct deleter : public deleter_base {        deleter(Deleter d) : d_(d) {}        virtual void apply(void* p) { d_(static_cast<T*>(p)); }        Deleter d_;    };    public:    template <typename Deleter>         smartptr(T* p, Deleter d) :            p_(p), d_(new deleter<Deleter>(d)) {}    ~smartptr() { d_->apply(p_); delete d_; } T* operator->() ...