boost::any

boost::any is a strong concept and a much better replacement to void* to hold any type of data. You can make heterogenous containers using it as well. Let us see how it works in a very simplified way. The idea is to have a template class that can wrap all types and a value associated with that type. Something like this:

template<typename T>
class HoldData
{
    T t;
};

And then having a base class from which this wrapper would derive, so the above becomes adding a constructor that needs the type to be stored in it to be copy constructible:

class BaseHolder
{
    public:
        virtual ~BaseHolder(){}
};

template<typename T>
class HoldData : public BaseHolder
{
    public:
        HoldData(const T& t_) : t(t_){}
    private:
        T t;
};

Now, you would have a class, name it Variant that will take inputs of all types and then has a pointer to this wrapper's base type. So, now you have (including above classes):

class BaseHolder
{
    public:
        virtual ~BaseHolder(){}
};

template<typename T>
class HoldData : public BaseHolder
{
    public:
        HoldData(const T& t_) : t(t_){}
    private:
        T t;
};

class Variant
{
    public:
        template<typename T>
        Variant(const T& t) : data(new HoldData<T>(t)){}
        ~Variant(){delete data;}
    private:
        BaseHolder* data;
};

You construct the corresponding type's wrapper objects and save their pointer into the another class that you call variant, that can hold and help retrieve any data type and does not lose the respective type information. That is actually what boost::any does. Take a look at the code here - boost::any code.

The documentation on it can be found here - boost::any documentation.