设计模式实现（二）——策略模式的C++实现

 1 #ifndef STRATEGY_H
 2 #define STRATEGY_H
 3 
 4 class Strategy {
 5 public:
 6     Strategy() = default;
 7     virtual ~Strategy()
 8     {
 9     }
10     virtual int DoOperation(int x, int y) = 0;
11 };
12 #endif // !STRATEGY_H

 1 #pragma once
 2 #include "Strategy .h"
 3 class OperationAdd :
 4     public Strategy
 5 {
 6 public:
 7     OperationAdd();
 8     ~OperationAdd();
 9     int DoOperation(int x, int y) override;
10 };

 1 #include "pch.h"
 2 #include "OperationAdd.h"
 3 
 4 
 5 OperationAdd::OperationAdd()
 6 {
 7 }
 8 
 9 
10 OperationAdd::~OperationAdd()
11 {
12 }
13 
14 int OperationAdd::DoOperation(int x, int y)
15 {
16     return x + y;
17 }

 1 #pragma once
 2 #include "Strategy .h"
 3 class OperationSubstract :
 4     public Strategy
 5 {
 6 public:
 7     OperationSubstract();
 8     ~OperationSubstract();
 9     int DoOperation(int x, int y) override;
10 };

 1 #include "pch.h"
 2 #include "OperationSubstract.h"
 3 
 4 OperationSubstract::OperationSubstract()
 5 {
 6 }
 7 
 8 
 9 OperationSubstract::~OperationSubstract()
10 {
11 }
12 
13 int OperationSubstract::DoOperation(int x, int y)
14 {
15     return x - y;
16 }

 1 #pragma once
 2 #include "Strategy .h"
 3 class OperationMultiply :
 4     public Strategy
 5 {
 6 public:
 7     OperationMultiply();
 8     ~OperationMultiply();
 9     int DoOperation(int x, int y) override;
10 };

 1 #include "pch.h"
 2 #include "OperationMultiply.h"
 3 
 4 OperationMultiply::OperationMultiply()
 5 {
 6 }
 7 
 8 OperationMultiply::~OperationMultiply()
 9 {
10 }
11 
12 int OperationMultiply::DoOperation(int x, int y)
13 {
14     return x * y;
15 }

 1 #ifndef CONTEXT_H
 2 #define CONTEXT_H
 3 #include "Strategy .h"
 4 
 5 class Context {
 6 public:
 7     Context(Strategy *strategy);
 8     ~Context() = default;
 9     int ExecuteStrategy(int x, int y);
10 private:
11     Strategy *strategy;
12 };
13 #endif // !CONTEXT_H

 1 #include "pch.h"
 2 #include "Context .h"
 3 
 4 Context::Context(Strategy * strategy)
 5 {
 6     this->strategy = strategy;
 7 }
 8 
 9 int Context::ExecuteStrategy(int x, int y)
10 {
11     return this->strategy->DoOperation(x, y);
12 }

 1 // StrategyDemo.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
 2 //
 3 
 4 #include "pch.h"
 5 #include <iostream>
 6 #include <map>
 7 #include <string>
 8 #include "Context .h"
 9 #include "Strategy .h"
10 #include "OperationAdd.h"
11 #include "OperationMultiply.h"
12 #include "OperationSubstract.h"
13 using namespace std;
14  
15 std::map<string, Strategy*> strategyMap = 
16         { {"add", new (nothrow)OperationAdd},
17           {"sub", new (nothrow)OperationSubstract},
18           {"muti", new (nothrow)OperationMultiply}
19         };
20 
21 int main()
22 {
23     int num1, num2;
24     string operationName{};
25     cin >> operationName;
26     cin >> num1 >> num2;
27     Context context(strategyMap[operationName]);
28     cout << context.ExecuteStrategy(num1, num2) << endl;
29     return 0;
30 }