23种设计模式的C++实现

#include <iostream> using namespace std; class State; class ConcreteStateB; class ConcreteStateA; class State { public: virtual void OperationChangeState(Context*) = 0; virtual void OperationInterface(Context*) = 0; virtual ~State() { } protected: bool ChangeState(Context* con, State *st) { con->ChangeState(st); } }; class ConcreteStateA :public State { public: void OperationChangeState(Context* con) { OperationInterface(con); this->ChangeState(con, new ConcreteStateB()); } void OperationInterface(Context* con) { cout << "ConcreteStateA::OperationInterface..." << endl; } }; class ConcreteStateB :public State { public: void OperationChangeState(Context* con) { OperationInterface(con); this->ChangeState(con, new ConcreteStateA()); } void OperationInterface(Context* con) { cout << "ConcreteStateB::OperationInterface..." << endl; } }; class Context { public: Context(State* st) { _st = st; } void OperationInterface() { _st->OperationInterface(this); } void OperationChangeState() { _st->OperationInterface(this); } private: friend class State; bool ChangeState(State* st) { _st = st; return true; } State *_st; }; int main() { State *st = new ConcreteStateA(); Context *con = new Context(st); con->OperationInterface(); con->OperationInterface(); con->OperationInterface(); delete con; delete st; return 0; }