state模式

http://www.cnblogs.com/graphicsme/archive/2011/12/09/2282657.html
http://www.cnblogs.com/k-eckel/articles/204006.aspx
  1 #include <iostream>
  2 #include <string>
  3 #include <vector>
  4 #include <queue>
  5 #include <set>
  6 #include <algorithm>
  7 #include <map>
  8 #include <stack>
  9 using namespace std;
 10 class State;
 11 class Context {
 12 public:
 13     Context() {
 14     }
 15 
 16     Context(State* state);
 17 
 18     ~Context();
 19     void Handle();
 20 
 21     void OperationForStateA();
 22     void OperationForStateB();
 23     void ChangeState(State* state);
 24 
 25 private:
 26     State* _state;
 27 
 28 };
 29 
 30 class State {
 31 public:
 32     State() {
 33     }
 34 
 35     virtual ~State() {
 36     }
 37 
 38     virtual void Handle(Context* con) = 0;
 39 
 40 protected:
 41     void ChangeState(Context* con, State* st);
 42 
 43 };
 44 
 45 class ConcreteStateA: public State {
 46 public:
 47     ConcreteStateA() {
 48     }
 49 
 50     virtual ~ConcreteStateA() {
 51     }
 52 
 53     void Handle(Context* con);
 54 
 55 };
 56 
 57 class ConcreteStateB: public State {
 58 public:
 59     ConcreteStateB() {
 60     }
 61 
 62     virtual ~ConcreteStateB() {
 63     }
 64 
 65     void Handle(Context* con);
 66 
 67 };
 68 
 69 Context::Context(State* state) {
 70     this->_state = state;
 71 }
 72 
 73 Context::~Context() {
 74     delete _state;
 75 }
 76 
 77 void Context::Handle() {
 78     _state->Handle(this);
 79 }
 80 
 81 void Context::ChangeState(State* state) {
 82     this->_state = state;
 83 
 84 }
 85 
 86 void Context::OperationForStateA() {
 87     cout << "Do operation in State A ";
 88 }
 89 
 90 void Context::OperationForStateB() {
 91     cout << "Do operation in State B ";
 92 }
 93 
 94 void State::ChangeState(Context* con, State* st) {
 95     con->ChangeState(st);
 96 }
 97 
 98 void ConcreteStateA::Handle(Context* con) {
 99     con->OperationForStateA();
100 
101     cout << ":: State change from A to B" << endl;
102 
103     State::ChangeState(con, new ConcreteStateB());
104 }
105 
106 void ConcreteStateB::Handle(Context* con) {
107     con->OperationForStateB();
108 
109     cout << ":: State change from B to A" << endl;
110 
111     State::ChangeState(con, new ConcreteStateA());
112 }
113 
114 int main(int argc, char* argv[]) {
115     State* st = new ConcreteStateA();
116 
117     Context* con = new Context(st);
118 
119     con->Handle();
120     con->Handle();
121     con->Handle();
122 
123     if (con != NULL)
124         delete con;
125 
126     if (st != NULL)
127         st = NULL;
128 
129     return 0;
130 }