2022-06-29

C++之计算器类实现
优点：结构清晰，利于前期和后期的拓展和维护
example

#include <iostream>
#include <string>
using namespace std;

//抽象类：
class Calculator 
{
public:
	virtual int result() 
	{ 
		return 0;
	}

	int num1;
	int num2;
	 
};


class Add : public Calculator {
public:
	 int result()
	{
		return num1+num2;
	}
};
class Sub : public Calculator 
{
public:
	 int result()
	{
		return num1 - num2;
	}
};
class Mul : public Calculator {
public:
	 int result()
	{
		return num1 * num2;
	}
};

//函数
void test()
{
	//父类指针或者引用指向子类对象
	Calculator * abc = new Add;
	cout << "输入第一个数据：" << endl;
	cin>>abc->num1;
	cout << "输入第二个数据：" << endl;
	cin>>abc->num2;
	cout << abc->num1 << " + " << abc->num2 << " = " << abc->result() << endl;
	delete abc;

	abc = new Sub;
	cout << "输入第一个数据：" << endl;
	cin >> abc->num1;
	cout << "输入第二个数据：" << endl;
	cin >> abc->num2;
	cout << abc->num1 << " - " << abc->num2 << " = " << abc->result() << endl;
	delete abc;

	abc = new Mul;
	cout << "输入第一个数据：" << endl;
	cin >> abc->num1;
	cout << "输入第二个数据：" << endl;
	cin >> abc->num2;
	cout << abc->num1 << " *" << abc->num2 << " = " << abc->result() << endl;
	delete abc;
}
int main()
{
	test();
	system("pause");
	return 0;
}

错误记录：
第一次书写：

cout << abc->num1 << " + " << abc->num2 << " = " << abc->result << endl;

成员函数result未添加（）
VS2017显示：C3867 “XXXXX”，非标准语法，请使用&来创建指向成员的指针
编译器认为此未成员变量，不是成员函数。所以会显示这样的错误
修改成：

cout << abc->num1 << " + " << abc->num2 << " = " << abc->result() << endl;