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| // unique_ptr deleter with state #include <iostream> #include <memory> class state_deleter { // a deleter class with state int count_; public: state_deleter() : count_(0) {} template <class T> void operator()(T* p) { std::cout << "[deleted #" << ++count_ << "]\n"; delete p; } }; int main () { state_deleter del; std::unique_ptr<int> p; // uses default deleter // alpha and beta use independent copies of the deleter: std::unique_ptr<int,state_deleter> alpha (new int); std::unique_ptr<int,state_deleter> beta (new int,alpha.get_deleter()); // gamma and delta share the deleter "del" (deleter type is a reference!): std::unique_ptr<int,state_deleter&> gamma (new int,del); std::unique_ptr<int,state_deleter&> delta (new int,gamma.get_deleter()); std::cout << "resetting alpha..."; alpha.reset(new int); std::cout << "resetting beta..."; beta.reset(new int); std::cout << "resetting gamma..."; gamma.reset(new int); std::cout << "resetting delta..."; delta.reset(new int); std::cout << "calling gamma/delta deleter..."; gamma.get_deleter()(new int); alpha.get_deleter() = state_deleter(); // a brand new deleter for alpha // additional deletions when unique_ptr objects reach out of scope // (in inverse order of declaration) return 0; }
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