C++ 多态应用

偷偷拿来记录一下萌新的cs路——day 40 计算器类、制作饮品、电脑组装。

目录

计算器类

用普通类写法实现计算器

用多态实现计算器类

纯虚函数和抽象类实现制作饮品

组装电脑

组装电脑的框架

实现一台电脑

实现多台电脑

计算器类

用普通类写法实现计算器

#include
#include
using namespace std;

class Calculator {
public:
	int getResult(string oper) {
		if (oper == "+") {
			return m_Num1 + m_Num2;
		}
		else if (oper == "-") {
			return m_Num1 - m_Num2;
		}
		else if (oper == "*") {
			return m_Num1 * m_Num2;
		}
		else if (oper == "/") {
			return m_Num1 / m_Num2;
		}
	}
	int m_Num1;
	int m_Num2;
};

void test01() {
	Calculator c;
	c.m_Num1 = 10;  // 操作数1
	c.m_Num2 = 20;  // 操作数2

	cout << c.m_Num1 << " + " << c.m_Num2 << " = " << c.getResult("+") << endl;
	cout << c.m_Num1 << " - " << c.m_Num2 << " = " << c.getResult("-") << endl;
	cout << c.m_Num1 << " * " << c.m_Num2 << " = " << c.getResult("*") << endl;
	cout << c.m_Num1 << " / " << c.m_Num2 << " = " << c.getResult("/") << endl;
}

int main() {
	test01();
	return 0;
}

运行结果：

可见若要增加功能，需要修改Calculator 中的源码，不符合开发中的开闭原则。

多态的优点：代码组织结构清晰，可读性强，利于后期拓展及维护。

用多态实现计算器类

#include
#include
using namespace std;

// 计算器抽象类
class AbstractCalculator {
public:
	virtual int getResult() {
		return 0;
	}
	int m_Num1 = 0, m_Num2 = 0;
};

// 加法计算器类
class AddCalculator :public AbstractCalculator {
public:
	int getResult() {
		return m_Num1 + m_Num2;
	}
};

// 减法
class SubCalculator :public AbstractCalculator {
public:
	int getResult() {
		return m_Num1 - m_Num2;
	}
};

// 乘法
class MulCalculator :public AbstractCalculator {
public:
	int getResult() {
		return m_Num1 * m_Num2;
	}
};

void test02() {
	AbstractCalculator* abc = new AddCalculator;  // 父类指针指向子类对象
	abc->m_Num1 = 10;
	abc->m_Num2 = 20;
	cout << abc->m_Num1 << " + " << abc->m_Num2 << " = " << abc->getResult() << endl;
	
	delete abc;  // 释放堆区数据

	abc = new SubCalculator;
	abc->m_Num1 = 10;
	abc->m_Num2 = 20;
	cout << abc->m_Num1 << " - " << abc->m_Num2 << " = " << abc->getResult() << endl;
    
    delete abc;
	
	abc = new MulCalculator;
	abc->m_Num1 = 10;
	abc->m_Num2 = 20;
	cout << abc->m_Num1 << " * " << abc->m_Num2 << " = " << abc->getResult() << endl;
   
    delete abc;
}

int main() {
	test02();
	return 0;
}

堆区数据：由程序员控制，程序运行结束由编译器回收。

运行结果

纯虚函数和抽象类实现制作饮品

#include
using namespace std;

class AbstractDrinking {
public:
	virtual void  Boil() = 0;
	virtual void Brew() = 0;  // 冲泡
	virtual void PourInCup() = 0;
	virtual void PutSth() = 0;
	void makeDrink() {
		Boil();
		Brew();
		PourInCup();
		PutSth();
	}
};

class Coffee :public AbstractDrinking {
public:
	void  Boil() {
		cout << "Boil the water. " << endl;
	}
	void Brew() {
		cout << "Brew the coffee. " << endl;
	}
	void PourInCup() {
		cout << "Pour coffee into cups. " << endl;
	}
	void PutSth() {
		cout << "Pour in milk. " << endl;
	}
};

class Tea :public AbstractDrinking {
	virtual void  Boil() {
		cout << "Boil the water. " << endl;
	}
	virtual void Brew() {
		cout << "Brew the tea leaves. " << endl;
	}
	virtual void PourInCup() {
		cout << "Pour tea into cups. " << endl;
	}
	virtual void PutSth() {
		cout << "Pour in wolfberries and lemon. " << endl;
	}
};

// 制作过程
void doWork(AbstractDrinking *abs) {
	abs->makeDrink();
	delete abs;  // 释放堆区数据，防止泄露
}

void test01() {
	doWork(new Coffee);
	cout << endl;  // 分割
	doWork(new Tea);
}

int main() {
	test01();
	return 0;
}

运行结果

组装电脑

组装电脑的框架

最终目的：实现三台不同cpu、显卡、内存条组合的电脑。

#include
using namespace std;

class CPU {
	virtual void calculate() = 0;
};

// 显卡
class GraphicsCard {
	virtual void display() = 0;
};

// 内存条
class RAM {
	virtual void storage() = 0;
};

class Computer {
	Computer() {

	}
};

class IntelCPU : public CPU {
	void calculate() {
		cout << "CPU of Intel. " << endl;
	}
};

class AMDCPU : public CPU {
	void calculate() {
		cout << "CPU of AMD. " << endl;
	}
};

class IntelGraphicsCard : public GraphicsCard {
	void display() {
		cout << "Graphics card of Intel. " << endl;
	}
};

class SamsungGraphicsCard : public GraphicsCard {
	void display() {
		cout << "Graphics card of Samsung. " << endl;
	}
};

class KinstonRAM : public RAM {
	void storage() {
		cout << "RAM of Kingston. " << endl;
	}
};

class SamsungRAM : public RAM {
	void storage() {
		cout << "RAM of Samsung. " << endl;
	}
};

void test01() {

}

int main() {
	test01();
	return 0;
}

实现一台电脑

#include
using namespace std;

class CPU {
public:
	virtual void calculate() = 0;
};

// 显卡
class GraphicsCard {
public:
	virtual void display() = 0;
};

// 内存条
class RAM {
public:
	virtual void storage() = 0;
};

class Computer {
public:
	// 接收指针
	Computer(CPU* cpu, GraphicsCard* gc, RAM* ram) {
		m_cpu = cpu;
		m_gc = gc;
		m_ram = ram;
	}
	// 工作函数
	void work() {
		m_cpu->calculate();
		m_gc->display();
		m_ram->storage();
	}
private:
	CPU* m_cpu;
	GraphicsCard* m_gc;
	RAM* m_ram;
};

class IntelCPU : public CPU {
public:
	void calculate() {
		cout << "CPU of Intel. " << endl;
	}
};

class AMDCPU : public CPU {
public:
	void calculate() {
		cout << "CPU of AMD. " << endl;
	}
};

class IntelGraphicsCard : public GraphicsCard {
public:
	void display() {
		cout << "Graphics card of Intel. " << endl;
	}
};

class SamsungGraphicsCard : public GraphicsCard {
public:
	void display() {
		cout << "Graphics card of Samsung. " << endl;
	}
};

class KingstonRAM : public RAM {
public:
	void storage() {
		cout << "RAM of Kingston. " << endl;
	}
};

class SamsungRAM : public RAM {
public:
	void storage() {
		cout << "RAM of Samsung. " << endl;
	}
};

void test01() {
	// 第一台电脑部件
	CPU* intelCPU = new IntelCPU;
	GraphicsCard* intelGc = new IntelGraphicsCard;
	RAM* kingstonRAM = new KingstonRAM;

	// 创建第一台电脑
	Computer* computer1 = new Computer(intelCPU, intelGc, kingstonRAM);
	computer1->work();
	delete computer1;
}	


int main() {
	test01();
	return 0;
}

运行结果：

实现多台电脑

由于部件的指针未被释放，创建第二台电脑需要先释放部件指针，可以直接在delete computer1 后释放也可以在Computer 类中定义析构函数。

class Computer {
public:
	Computer(CPU* cpu, GraphicsCard* gc, RAM* ram) {
		m_cpu = cpu;
		m_gc = gc;
		m_ram = ram;
	}
	void work() {
		m_cpu->calculate();
		m_gc->display();
		m_ram->storage();
	}
	// 析构函数释放电脑部件
	~Computer() {
		if (m_cpu != NULL) {
			delete m_cpu;
			m_cpu = NULL;
		}
		if (m_gc != NULL) {
			delete m_gc;
			m_gc = NULL;
		}
		if (m_ram != NULL) {
			delete m_ram;
			m_ram = NULL;
		}
	}
private:
	CPU* m_cpu;
	GraphicsCard* m_gc;
	RAM* m_ram;
};

完整代码：

#include
using namespace std;

class CPU {
public:
	virtual void calculate() = 0;
};

// 显卡
class GraphicsCard {
public:
	virtual void display() = 0;
};

// 内存条
class RAM {
public:
	virtual void storage() = 0;
};

class Computer {
public:
	// 接收指针
	Computer(CPU* cpu, GraphicsCard* gc, RAM* ram) {
		m_cpu = cpu;
		m_gc = gc;
		m_ram = ram;
	}
	// 工作函数
	void work() {
		m_cpu->calculate();
		m_gc->display();
		m_ram->storage();
	}
	// 析构函数释放电脑部件
	~Computer() {
		if (m_cpu != NULL) {
			delete m_cpu;
			m_cpu = NULL;
		}
		if (m_gc != NULL) {
			delete m_gc;
			m_gc = NULL;
		}
		if (m_ram != NULL) {
			delete m_ram;
			m_ram = NULL;
		}
	}
private:
	CPU* m_cpu;
	GraphicsCard* m_gc;
	RAM* m_ram;
};

class IntelCPU : public CPU {
public:
	void calculate() {
		cout << "CPU of Intel. " << endl;
	}
};

class AMDCPU : public CPU {
public:
	void calculate() {
		cout << "CPU of AMD. " << endl;
	}
};

class IntelGraphicsCard : public GraphicsCard {
public:
	void display() {
		cout << "Graphics card of Intel. " << endl;
	}
};

class SamsungGraphicsCard : public GraphicsCard {
public:
	void display() {
		cout << "Graphics card of Samsung. " << endl;
	}
};

class KingstonRAM : public RAM {
public:
	void storage() {
		cout << "RAM of Kingston. " << endl;
	}
};

class SamsungRAM : public RAM {
public:
	void storage() {
		cout << "RAM of Samsung. " << endl;
	}
};

void test01() {
	// 第一台电脑部件
	CPU* intelCPU = new IntelCPU;
	GraphicsCard* intelGc = new IntelGraphicsCard;
	RAM* kingstonRAM = new KingstonRAM;

	// 创建第一台电脑
	Computer* computer1 = new Computer(intelCPU, intelGc, kingstonRAM);
	computer1->work();
	delete computer1;

	cout << endl;

	

	Computer* computer2 = new Computer(new IntelCPU, new SamsungGraphicsCard, new KingstonRAM);
	computer2->work();
	delete computer2;

	cout << endl;

	Computer* computer3 = new Computer(new AMDCPU, new IntelGraphicsCard, new SamsungRAM);
	computer3->work();
	delete computer3;
}	


int main() {
	test01();
	return 0;
}

运行结果：

 

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