设计模式（二）：策略模式

 1 #include<iostream>
 2 #include<string.h>
 3 #include<stdio.h>
 4 #include<stdlib.h>
 5 using namespace std;
 6 
 7 /*
 8 设计模式（二）：策略模式
 9 定义一系列的算法，把他们一个个封装起来，并且使他们可相互替换。
10 该模式使得算法可独立于使用他的客户而变化.
11 */
12 
13 typedef enum StrategyType{ StrategyA, StrategyB, StrategyC }STRATEGYTYPE;
14 //抽象算法策略-基类
15 class Strategy
16 {
17 public:
18     virtual void AlgorithmInterface() = 0;
19     virtual ~Strategy(){}
20 };
21 
22 class ConcretStrategyA :public Strategy
23 {
24 public:
25     void AlgorithmInterface(){ cout << "I am from ConcretStrategyA" << endl; }
26     ~ConcretStrategyA(){}
27 };
28 
29 class ConcretStrategyB :public Strategy
30 {
31 public:
32     void AlgorithmInterface(){ cout << "I am from ConcretStrategyB" << endl; }
33     ~ConcretStrategyB(){}
34 };
35 
36 class ConcretStrategyC :public Strategy
37 {
38 public:
39     void AlgorithmInterface(){ cout << "I am from ConcretStrategyC" << endl; }
40     ~ConcretStrategyC(){}
41 };
42 
43 
44 class Context
45 {
46 public:
47     Context(STRATEGYTYPE strategyType)
48     {
49         switch (strategyType)
50         {
51         case StrategyA:
52             strategy = new ConcretStrategyA();
53             break;
54         case StrategyB:
55             strategy = new ConcretStrategyB();
56             break;
57         case StrategyC:
58             strategy = new ConcretStrategyC();
59             break;
60         default:
61             strategy = new ConcretStrategyA();
62             break;
63         }
64     }
65 
66     ~Context()
67     {
68         if (strategy)
69             delete strategy;
70     }
71 
72     void GetInterface()
73     {
74         if (strategy)
75             strategy->AlgorithmInterface();
76     }
77 private:
78     Strategy* strategy;
79 
80 };
81 
82 int main(int argc,char** argv)
83 {
84     Context* tmp = new Context(StrategyA);
85     tmp->GetInterface();
86     if (tmp)
87         delete tmp;
88     system("pause");
89     return 0;
90 }