Restoring any type

are there any ways to restore type of packed into boost::any object? If now, can I store some association map for it? I need something like (pseudocode):

map<key, any> someMap;
someMap["Ke开发者_JS百科y"] = some own object;
getType("Key");

Not arbitrarily, you need to have some static type(s) you want to work with in C++.

So you can test for or cast to a specific type using any::type() and any_cast(), e.g.:

const boost::any& any = someMap["Key"].type();
if (int* i = boost::any_cast<int>(&any)) {
    std::cout << *i << std::endl;
} else if (double* d = boost::any_cast<double>(&any)) {
// ...

But something like the following can not be done in general due to C++ being statically typed:

magically_restore_type(someMap["Key"]).someMethod();

Using something like boost::any in C++ is almost always not a good idea, exactly because handling arbitrary types is no fun. If you only need to handle a known finite set of types, don't use boost::any - there are better options like boost::variant or polymorphic classes.

Are you trying to get the type of the value, or just cast it back to what it was? If you just want to cast it, just use boost::any_cast:

boost::any val = someMap["Key"];
RealType* r = boost::any_cast<RealType>(&val);

Let's say you did have such a function to extract the correctly-typed extraction from a boost::any. What would the return value of this function be? What would your code look like?

// Extracts v and returns the correct type... except we can't do that in C++. Let's just call it MagicalValue for now.
MagicalValue magic(const boost::any& v);

void perform_magic(const boost::any& v)
{
    MagicalValue r = magic(v);
    r.hello_world();    // Wait, what?
}

You can't do this type of trickery in statically-typed languages. What you can try is polymorphism instead of boost::any. This gives you a common interface you CAN use in C++.