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//
// Copyright (c) Chris Glover, 2016.
//
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
//[type_index_runtime_cast_example
/*`
The following example shows that `runtime_cast` is able to find a valid pointer
in various class hierarchies regardless of inheritance or type relation.
Example works with and without RTTI."
*/
#include <boost/type_index/runtime_cast.hpp>
#include <iostream>
struct A {
BOOST_TYPE_INDEX_REGISTER_RUNTIME_CLASS(BOOST_TYPE_INDEX_NO_BASE_CLASS)
virtual ~A()
{}
};
struct B {
BOOST_TYPE_INDEX_REGISTER_RUNTIME_CLASS(BOOST_TYPE_INDEX_NO_BASE_CLASS)
virtual ~B()
{}
};
struct C : A {
BOOST_TYPE_INDEX_REGISTER_RUNTIME_CLASS((A))
};
struct D : B {
BOOST_TYPE_INDEX_REGISTER_RUNTIME_CLASS((B))
};
struct E : C, D {
BOOST_TYPE_INDEX_REGISTER_RUNTIME_CLASS((C)(D))
};
int main() {
C c;
A* a = &c;
if(C* cp = boost::typeindex::runtime_cast<C*>(a)) {
std::cout << "Yes, a points to a C: "
<< a << "->" << cp << '\n';
}
else {
std::cout << "Error: Expected a to point to a C" << '\n';
}
if(E* ce = boost::typeindex::runtime_cast<E*>(a)) {
std::cout << "Error: Expected a to not points to an E: "
<< a << "->" << ce << '\n';
}
else {
std::cout << "But, a does not point to an E" << '\n';
}
E e;
C* cp2 = &e;
if(D* dp = boost::typeindex::runtime_cast<D*>(cp2)) {
std::cout << "Yes, we can cross-cast from a C* to a D* when we actually have an E: "
<< cp2 << "->" << dp << '\n';
}
else {
std::cout << "Error: Expected cp to point to a D" << '\n';
}
/*`
Alternatively, we can use runtime_pointer_cast so we don't need to specity the target as a pointer.
This works for smart_ptr types too.
*/
A* ap = &e;
if(B* bp = boost::typeindex::runtime_pointer_cast<B>(ap)) {
std::cout << "Yes, we can cross-cast and up-cast at the same time."
<< ap << "->" << bp << '\n';
}
else {
std::cout << "Error: Expected ap to point to a B" << '\n';
}
return 0;
}
//] [/type_index_runtime_cast_example]
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