《大话设计模式》之简单工厂模式

 1 #ifndef _CALCULATOR_H_
 2 #define _CALCULATOR_H_
 3 #include <string>
 4 
 5 struct Calculator {
 6     Calculator() = default;
 7     Calculator(double lNum, double rNum) 
 8         :leftNumber(lNum), rightNumber(rNum), result(0){}
 9     ~Calculator(){}
10 
11     virtual double getResult() = 0; //基类中可实现也可不实现
12 protected:
13     double leftNumber;
14     double rightNumber;
15     double result;
16 };
17 
18 /*
19 关于继承方式：
20     public     -- 属性不变
21     protected  -- public变成protected
22     private    -- 都变成private
23 */
24 class CalculatorAdd :public Calculator
25 {
26 public:
27     CalculatorAdd() = default;
28     CalculatorAdd(double lNum, double rNum) 
29         :Calculator(lNum, rNum){}
30     ~CalculatorAdd(){};
31     //加
32     virtual double getResult();
33 };
34 class CalculatorSub :public Calculator
35 {
36 public:
37     CalculatorSub() = default;
38     CalculatorSub(double lNum, double rNum) 
39         :Calculator(lNum, rNum){}
40     ~CalculatorSub(){};
41     //减
42     virtual double getResult();
43 };
44 class CalculatorMul :public Calculator
45 {
46 public:
47     CalculatorMul() = default;
48     CalculatorMul(double lNum, double rNum) 
49         :Calculator(lNum, rNum){}
50     ~CalculatorMul(){};
51     //乘
52     virtual double getResult();
53 };
54 class CalculatorDiv :public Calculator
55 {
56 public:
57     CalculatorDiv() = default;
58     CalculatorDiv(double lNum, double rNum)
59         :Calculator(lNum, rNum){}
60     ~CalculatorDiv(){};
61     //除
62     virtual double getResult();
63 };
64 
65 struct FactoryCalculator {
66     FactoryCalculator() = default;
67     FactoryCalculator(std::string op, double num1, double num2);
68     double getResult(){ return p->getResult(); }//简短函数默认inline
69 private:
70     std::string operate;
71     double number1;
72     double number2;
73     Calculator *p;
74 };
75 
76 #endif

 1 #include "calculator.h"
 2 #include <iostream>
 3 
 4 using namespace std; //通常，using只出现在源文件中，而不出现在头文件中
 5 
 6 double Calculator::getResult()
 7 {
 8     cout << "message print in Calculator::getResult" << endl;
 9     return 0.0;
10 }
11 
12 double CalculatorAdd::getResult()
13 {
14     Calculator::getResult();//我曾经来过
15 
16     result = leftNumber + rightNumber;
17     return result;
18 }
19 double CalculatorSub::getResult()
20 {
21     Calculator::getResult();
22 
23     result = leftNumber - rightNumber;
24     return result;
25 }
26 double CalculatorMul::getResult()
27 {
28     Calculator::getResult();
29 
30     result = leftNumber * rightNumber;
31     return result;
32 }
33 double CalculatorDiv::getResult()
34 {
35     Calculator::getResult();
36 
37     if (rightNumber == 0){
38         cout << "division cannot be zero" << endl;
39         return -1;
40     }
41     result = leftNumber / rightNumber;
42     return result;
43 }
44 
45 //如果函数体太长，则初始化列表就写在源文件（初始化列表必须跟函数体）
46 FactoryCalculator::FactoryCalculator(string op, double num1, double num2) 
47     :operate(op), number1(num1), number2(num2)
48 {
49     char flag = operate[0];
50     switch (flag)
51     {
52     case ‘+‘:
53         p = new CalculatorAdd(number1, number2);
54         break;
55     case ‘-‘:
56         p = new CalculatorSub(number1, num2);
57         break;
58     case ‘*‘:
59         p = new CalculatorMul(number1, number2);
60         break;
61     case ‘/‘:
62         p = new CalculatorDiv(number1, number2);
63         break;
64     default:
65         break;
66     }
67 }

 1 #include "calculator.h"
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     FactoryCalculator *factoryCalculaotr = new FactoryCalculator("+", 1, 2);
 9     FactoryCalculator *factoryCalculaotr2 = new FactoryCalculator("-", 1, 2);
10     FactoryCalculator *factoryCalculaotr3 = new FactoryCalculator("*", 1, 2);
11     FactoryCalculator *factoryCalculaotr4 = new FactoryCalculator("/", 1, 2);
12     cout << factoryCalculaotr->getResult() << endl;
13     cout << factoryCalculaotr2->getResult() << endl;
14     cout << factoryCalculaotr3->getResult() << endl;
15     cout << factoryCalculaotr4->getResult() << endl;
16 
17     system("pause");
18 }