//: C12:CopyingWithPointers.cpp // From Thinking in C++, 2nd Edition // Available at http://www.BruceEckel.com // (c) Bruce Eckel 2000 // Copyright notice in Copyright.txt // Solving the pointer aliasing problem by // duplicating what is pointed to during // assignment and copy-construction. #include "../require.h" #include #include using namespace std; class Dog { string nm; public: Dog(const string& name) : nm(name) { cout << "Creating Dog: " << *this << endl; } // Synthesized copy-constructor & operator= // are correct. // Create a Dog from a Dog pointer: Dog(const Dog* dp, const string& msg) : nm(dp->nm + msg) { cout << "Copied dog " << *this << " from " << *dp << endl; } ~Dog() { cout << "Deleting Dog: " << *this << endl; } void rename(const string& newName) { nm = newName; cout << "Dog renamed to: " << *this << endl; } friend ostream& operator<<(ostream& os, const Dog& d) { return os << "[" << d.nm << "]"; } }; class DogHouse { Dog* p; string houseName; public: DogHouse(Dog* dog, const string& house) : p(dog), houseName(house) {} DogHouse(const DogHouse& dh) : p(new Dog(dh.p, " copy-constructed")), houseName(dh.houseName + " copy-constructed") {} DogHouse& operator=(const DogHouse& dh) { // Check for self-assignment: if(&dh != this) { p = new Dog(dh.p, " assigned"); houseName = dh.houseName + " assigned"; } return *this; } void renameHouse(const string& newName) { houseName = newName; } Dog* getDog() const { return p; } ~DogHouse() { delete p; } friend ostream& operator<<(ostream& os, const DogHouse& dh) { return os << "[" << dh.houseName << "] contains " << *dh.p; } }; int main() { DogHouse fidos(new Dog("Fido"), "FidoHouse"); cout << fidos << endl; DogHouse fidos2 = fidos; // Copy construction cout << fidos2 << endl; fidos2.getDog()->rename("Spot"); fidos2.renameHouse("SpotHouse"); cout << fidos2 << endl; fidos = fidos2; // Assignment cout << fidos << endl; fidos.getDog()->rename("Max"); fidos2.renameHouse("MaxHouse"); } ///:~