Question

I’m trying to implement boost::any like class:

struct any
{
private:
struct holderBase
{
    virtual ~holderBase(){}
};

template<typename T>
struct holder : public holderBase
{
    T content;
    holder(const T& value) : content(value){}
    holder(const holder<T>& other) : content(other.content){}
};

holderBase *hl;
public:
template<typename T>
any(const T& data = T()) { hl = new holder<T>(data); }
any(const any& other) { hl = other.hl; }

template<typename T>
T get()
{
    if(holder<T>* p_hl = dynamic_cast<holder<T>*>(hl))
        return p_hl->content;
    else
        throw std::runtime_error("std::runtime_error");
}
};

I use a holder class (inherited by holderBase) to store the data.
How can I modify the any::get() function (or even modify the whole code) so that it doesn’t need a template parameter (the get() function)?

Answer 1

Stating the obvious: If you don’t want to return 1 particular type to the user then it needs to be templated. There’s nothing you can do about it.