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//Download by http://www.NewXing.com /* * This file contains code from "C++ Primer, Fourth Edition", by Stanley B. * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the * copyright and warranty notices given in that book: * * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo." * * * "The authors and publisher have taken care in the preparation of this book, * but make no expressed or implied warranty of any kind and assume no * responsibility for errors or omissions. No liability is assumed for * incidental or consequential damages in connection with or arising out of the * use of the information or programs contained herein." * * Permission is granted for this code to be used for educational purposes in * association with the book, given proper citation if and when posted or * reproduced.Any commercial use of this code requires the explicit written * permission of the publisher, Addison-Wesley Professional, a division of * Pearson Education, Inc. Send your request for permission, stating clearly * what code you would like to use, and in what specific way, to the following * address: * * Pearson Education, Inc. * Rights and Contracts Department * 75 Arlington Street, Suite 300 * Boston, MA 02216 * Fax: (617) 848-7047 */ #include <typeinfo> using std::bad_cast; #include <iostream> using std::cout; using std::endl; void exercises() { struct A { virtual ~A() { } }; struct B : virtual public A { /* ... */ }; struct C : public B { /* ... */ }; struct D : public B, virtual public A { /* ... */ }; A *pa = new C; if (B *pb = dynamic_cast< B* >(pa)) cout << "cast from C to B* ok" << endl; else cout << "cast from C to B* not ok" << endl; B *pb = new B; if (C *pc = dynamic_cast< C* >(pb)) cout << "cast from B to C* ok" << endl; else cout << "cast from B to C* not ok" << endl; A *pc = new C; if (B *pb = dynamic_cast< B* >(pc)) cout << "cast C to B* ok" << endl; else cout << "cast C to B* not ok" << endl; A *pd = new D; if (B *pb = dynamic_cast< B* >(pd)) cout << "cast D to B* ok" << endl; else cout << "cast D to B* not ok" << endl; } struct Base { virtual void f() {}; virtual ~Base() {}; }; struct Derived: public Base { }; int main() { Base *basePtr; basePtr = new Derived; // basePtr actually points to a Derived object if (Derived *derivedPtr = dynamic_cast<Derived*>(basePtr)) { // use the Derived object to which derivedPtr points } else { // BasePtr points at a Base object // use the Base object to which basePtr points } exercises(); } void f(const Base &b) { try { const Derived &d = dynamic_cast<const Derived&>(b); // use the Derived object to which b referred } catch (bad_cast) { // handle the fact that the cast failed } }