C++ --多态之实现一个计算器

一、多态实现一个计算器

• 多态的优点：组织结构清晰，可读性好，方便扩展和维护

分别使用，普通和多态实现一个计算器，体会一下多态带来的好处

1.1 普通实现

//多态的优点：组织结构清晰，可读性好，方便扩展和维护
//分别使用，普通和多态实现一个计算器，体会一下多态带来的好处
//普通实现
#include 
using namespace std;
#include 
class Calculator
{
public:
	int num1;
	int num2;
	//只有加减乘运算，如果后续需要增加减法，需要修改compute函数代码，不易扩展和维护
	int compute(string operation)
	{
		if (operation == "+")
			return num1 + num2;
		else if (operation == "-")
			return num1 - num2;
		else if (operation == "*")
			return num1 * num2;
		else
		{
			cout << "NO this Operation,Error\n";
			exit;
		}
	}
};
void test()
{
	Calculator c;
	c.num1 = 100;
	c.num2 = 200;
	cout << c.compute("+") << endl << c.compute("-") << endl << c.compute("*") << endl;
}
int main()
{
	test();
	return 0;
}

1.2 多态实现

#include 
using namespace std;
//多态来实现计算器
class AbstractCalculator
{
public:
	int num1;
	int num2;
	//虚函数，用户实现多态
	virtual int compute()
	{
		return 0;
	}
};
class AddCalculator : public AbstractCalculator
{
public:
	virtual int compute()
	{
		return num1 + num2;
	}
};
class DelCalculator : public AbstractCalculator
{
public:
	virtual int compute()
	{
		return num1 - num2;
	}
};
class MulCalculator : public AbstractCalculator
{
public:
	int compute()
	{
		return num1 * num2;
	}
};
//这里可以很方便的来扩展除法，而不需要修改上面的代码。如果哪个出现问题可以快速定位
class DivCalculator : public AbstractCalculator
{
public:
	int compute()
	{
		return num1 / num2;
	}
};
void test2()
{
	AbstractCalculator* abc = new AddCalculator;
	abc->num1 = 200;
	abc->num2 = 100;
	cout << abc->compute() << endl;
	delete abc;

	abc = new DelCalculator;
	abc->num1 = 200;
	abc->num2 = 100;
	cout << abc->compute() << endl;
	delete abc;

	abc = new MulCalculator;
	abc->num1 = 200;
	abc->num2 = 100;
	cout << abc->compute() << endl;
	delete abc;

	abc = new DivCalculator;
	abc->num1 = 200;
	abc->num2 = 100;
	cout << abc->compute() << endl;
	delete abc;
}
int main()
{
	test2();
	return 0;
}