1 //多态案例 -计算器类（普通写法  和 多态写法）
  2 
  3 #include <iostream>
  4 #include <string>
  5 using namespace std;
  6 
  7 //普通实现
  8 class Calualtor
  9 {
 10 public:
 11 
 12     int getResult(string oper)
 13     {
 14         if (oper == "+")
 15         {
 16             return m_Num1 + m_Num2;
 17         }
 18         else if (oper == "-")
 19         {
 20             return m_Num1 - m_Num2;
 21         }
 22         else if (oper == "*")
 23         {
 24             return m_Num1 * m_Num2;
 25         }
 26         //如果想扩展新的功能，需要修改源码
 27         //在真实的开发中   提倡 开闭原则
 28         //开闭原则：对扩展进行开放  对修改进行关闭
 29     }
 30 
 31 
 32     int m_Num1;   //操作数1
 33     int m_Num2;   //操作数2
 34 };
 35 
 36 void test01()
 37 {
 38     //创建计算器的对象
 39     Calualtor c;
 40     c.m_Num1 = 10;
 41     c.m_Num2 = 10;
 42 
 43     cout << c.m_Num1 << "+" << c.m_Num2 << "=" << c.getResult("+") << endl;
 44 
 45     cout << c.m_Num1 << "-" << c.m_Num2 << "=" << c.getResult("-") << endl;
 46 
 47     cout << c.m_Num1 << "*" << c.m_Num2 << "=" << c.getResult("*") << endl;
 48 }
 49 
 50 
 51 //利用多态实现计算器
 52 //多态好处：
 53 //1.组织结构清晰
 54 //2.可读性强
 55 //3.对于前期和后期扩展以及维护性高
 56 
 57 
 58 //实现计算器的抽象类
 59 class AbstractCalculator
 60 {
 61 public:
 62 
 63     virtual int getResult()
 64     {
 65         return 0;
 66     }
 67 
 68     int m_Num1;
 69     int m_Num2;
 70 };
 71 
 72 //加法计算器
 73 class AddCalculator : public AbstractCalculator
 74 {
 75 
 76 public:
 77     virtual int getResult()
 78     {
 79         return m_Num1 + m_Num2;
 80     }
 81 };
 82 
 83 //减法计算器
 84 class SubCalculator : public AbstractCalculator
 85 {
 86 
 87 public:
 88     virtual int getResult()
 89     {
 90         return m_Num1 - m_Num2;
 91     }
 92 };
 93 //乘法计算器
 94 class MulCalculator : public AbstractCalculator
 95 {
 96 
 97 public:
 98     virtual int getResult()
 99     {
100         return m_Num1 * m_Num2;
101     }
102 };
103 
104 
105 void test02()
106 {
107     //多态使用条件
108 
109     //父类指针或者引用指向子类对象
110     //加法运算
111     AbstractCalculator* abc = new  AddCalculator;
112     abc->m_Num1 = 10;
113     abc->m_Num2 = 20;
114     cout << "多态计算器" << endl;
115     cout << abc->m_Num1 << "+" << abc->m_Num2 << "=" << abc->getResult() << endl;
116 
117     //用完后销毁
118     delete abc;
119 
120     //减法运算
121     abc = new SubCalculator;
122     abc->m_Num1 = 100;
123     abc->m_Num2 = 101;
124     cout << abc->m_Num1 << "-" << abc->m_Num2 << "=" << abc->getResult() << endl;
125     delete abc;
126 
127     abc = new MulCalculator;
128     abc->m_Num1 = 12;
129     abc->m_Num2 = 10;
130     cout << abc->m_Num1 << "*" << abc->m_Num2 << "=" << abc->getResult() << endl;
131 
132     delete abc;
133 }
134 
135 int main()
136 {
137 
138     test01();
139     
140     test02();
141 
142     system("pause");
143 
144     return 0;
145 
146 }