C++类和对象之多态详解

#include <iostream>
using namespace std;
//动态多态满足条件
//1、有继承关系
//2、子类重写父类的虚函数 重写是指返回值 函数名 参数完全一样    重载是指函数名相同
//动态多态使用
//父类的指针或引用，指向子类对象


//当子类重写父类的虚函数，子类中的虚函数表内部会替换成子类的虚函数地址，将&Animal::speak替换成&Cat::speak

//动物类
class Animal {
public:
	//虚函数
	virtual void speak(){
		cout << "动物在说话" << endl;
	}
};
//猫类
class Cat :public Animal {
public:
	void speak() {
		cout << "小猫在说话" << endl;
	}
};
//狗类
class Dog :public Animal {
public:
	void speak() {
		cout << "小狗在说话" << endl;
	}
};

//执行说话的函数
//地址早绑定，在编译阶段就确定了函数的地址
//虽然想让猫说话，但是这里输出了动物在说话   因为地址早绑定
//如果想让猫说话，这个函数的地址就不能提前绑定，需要在运行阶段进行绑定，也即地址晚绑定
void DoSpeak(Animal &animal) {
	animal.speak();
}
void test01() {
	Cat cat;
	DoSpeak(cat);     //虽然想让猫说话，但是这里输出了动物在说话，因为地址早绑定，若父类改为虚函数地址晚绑定，就是猫在说话
	Dog dog;
	DoSpeak(dog);
}

void test02() {
	cout << "size of Animal = " << sizeof(Animal) << endl;
}
int main() {
	//test01();
	test02();
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;

//普通写法
class Calculate {
public:
	int GetResult(string oper) {
		if (oper == "+") {
			return num1 + num2;
		}
		else if (oper == "-") {
			return num1 - num2;
		}
		else if (oper == "*") {
			return num1 * num2;
		}
		//如果想扩展新的功能，需要修改原码，在实际开发中，提倡开闭原则：对扩展进行开发，对修改进行关闭
	}
	int num1;
	int num2;
};
void test01() {
	//创建计算器对象
	Calculate c;
	c.num1 = 10;
	c.num2 = 10;
	cout << c.num1 << " + "<< c.num2 << " = " <<c.GetResult("+") << endl;
	cout << c.num1 << " - "<< c.num2 << " = " <<c.GetResult("-") << endl;
	cout << c.num1 << " * "<< c.num2 << " = " <<c.GetResult("*") << endl;
}


//利用多态实现计算器
//多态的优点
//1、组织结构清晰
//2、可读性强
//3、对于前期扩展和后期维护性能高

//实现计算器抽象类
class AbstractCalculate {
public:
	virtual int Result() {
		return 0;
	}
	int m_num1;
	int m_num2;
};
//加法计算器类
class AddCalculate : public AbstractCalculate{
public:
	int Result() {
		return m_num1 + m_num2;
	}
};
//减法计算器类
class SubCalculate : public AbstractCalculate {
public:
	int Result() {
		return m_num1 - m_num2;
	}
};
//乘法计算器类
class MulCalculate : public AbstractCalculate {
public:
	int Result() {
		return m_num1 * m_num2;
	}
};
void test02() {
	//多态使用指针
	//父类指针或者引用指向子类对象

	//加法运算
	AbstractCalculate* p = new AddCalculate;
	p->m_num1 = 100;
	p->m_num2 = 100;
	cout << p->m_num1 << " + " << p->m_num2 << " = " << p->Result() <<endl;
	//用完后释放新开辟的堆区数据
	delete p;

	//减法运算
	p = new SubCalculate;
	p->m_num1 = 100;
	p->m_num2 = 100;
	cout << p->m_num1 << " - " << p->m_num2 << " = " << p->Result() << endl;
	delete p;

	//乘法运算
	p = new MulCalculate;
	p->m_num1 = 100;
	p->m_num2 = 100;
	cout << p->m_num1 << " * " << p->m_num2 << " = " << p->Result() << endl;
	delete p;
}
int main() {
	//test01();
	test02();
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
//纯虚函数语法 virtual 返回值 函数名（参数列表） = 0；
//当类中有了纯虚函数，这个类也称为抽象类，抽象类不能实例化对象，子类必须重写抽象类里的纯虚函数，不然子类也属于抽象类
class Base {
public:
	//纯虚函数 只要有纯虚函数这个类就是抽象类
	virtual void func() = 0;
};
class Son :public Base {
public:
	void func() {
		cout << "Son类下的func函数调用" << endl;
	}
};
void test01() {
	/*抽象类是无法实例化对象的
	Base b;
	new Base;*/
	Son s;
	s.func();
	//多态方式调用 父类的指针new一个子类
	Base* p = new Son;
	p->func();
	delete p;
}

int main() {
	test01();
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
class AbstractDrinking {
public:
	//煮水
	virtual void Boil() = 0;
	//冲泡
	virtual void Brew() = 0;
	//倒入杯中
	virtual void DropInCup() = 0;
	//加入辅料
	virtual void AddSomething() = 0;

	//制作饮品
	void MakeDrink() {
		Boil();
		Brew();
		DropInCup();
		AddSomething();
	}
};

//制作咖啡流程
class Coffee : public AbstractDrinking {
public:
	//煮水
	virtual void Boil() {
		cout << "煮一壶沸水" << endl;
	}
	//冲泡
	virtual void Brew() {
		cout << "冲泡咖啡粉" << endl;
	}
	//倒入杯中
	virtual void DropInCup() {
		cout << "将咖啡倒入杯中" << endl;
	}
	//加入辅料
	virtual void AddSomething() {
		cout << "将牛奶和白糖加入咖啡中" << endl;
	}
};


//制作茶水流程
class Tea : public AbstractDrinking {
public:
	//煮水
	virtual void Boil() {
		cout << "煮一壶沸水" << endl;
	}
	//冲泡
	virtual void Brew() {
		cout << "冲泡西湖龙井" << endl;
	}
	//倒入杯中
	virtual void DropInCup() {
		cout << "将茶水倒入杯中" << endl;
	}
	//加入辅料
	virtual void AddSomething() {
		cout << "将枸杞加入茶水中" << endl;
	}
};

//制作饮品函数
void DoWork(AbstractDrinking *p) {   //这里相当于 AbstractDrinking *p = new Coffee;
	                                //若这里不使用指针，改为引用，test01的函数就不能使用
	                               //因为引用是先实例化对象再调用对象，抽象类无法实例化对象
	p->MakeDrink();
	delete p;  //防止内存泄露，使用后记得释放内存
}
void test01() {
	//想喝一杯咖啡
	DoWork(new Coffee);
	cout << "-----------------------------------" << endl;
	//想喝一杯西湖龙井茶
	DoWork(new Tea);
}

int main() {
	test01();
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
//动物类
class Animal {
public:
	Animal() {
		cout << "这是Animal的构造函数调用" << endl;
	}
	//纯虚函数
	virtual void Speak() = 0;

	//为了走子类的虚构函数，需要将父类的虚构函数改为虚析构
	/*virtual ~Animal() {
		cout << "这是Animal的析构函数调用" << endl;
	}*/
	//纯虚析构函数  父类的堆区可能也被开辟需要释放，因此父类的析构也必须需要声明，也需要实现
	//有纯虚析构后这个类也属于抽象类，无法实例化对象
	virtual ~Animal() = 0;
};
Animal:: ~Animal() {
	cout << "这是Animal类的写在外部的纯虚析构函数调用" << endl;
}

//猫类
class Cat : public Animal{
public:
	//Cat类的构造函数
	Cat(string name) {
		cout << "这是Cat类的构造函数" << endl;
		m_name = new string(name);
	}
	void Speak() {
		cout << *m_name<<"小猫的叫声" << endl;
	}
	~Cat() {
		if (m_name != NULL) {
			//父类指针在析构的时候，不会调用子类中的析构函数，导致子类中有堆区开辟的数据没有被释放干净导致内存泄露
			cout << "这是Cat类的析构函数" << endl;
			delete m_name;
			m_name = NULL;
		}
	}
	string *m_name;
	
};

void test01() {
	Animal* p = new Cat("Tom");             //如果子类中没有堆区数据，可以不写虚析构或纯虚析构函数
	p->Speak();
	delete p;     //堆区开辟以后，释放指针
}

int main() {
	test01();
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
//每个零件都封装出抽象的基类
//CPU类
class Cpu {
public:
	//抽象的计算函数
	virtual void Calculate() = 0;
	//virtual ~Cpu() = 0; 
};
//Cpu::~Cpu() {
//	cout << "Cpu类写在外部的纯虚析构函数调用" << endl;
//}
//显卡类
class VideoCard {
public:
	//抽象的显示函数
	virtual void Display() = 0;
};
//内存条类
class Memory {
public:
	//抽象的存储函数
	virtual void Storage() = 0;
};


//电脑类
class Computer {
public:
	Computer(Cpu* cpu, VideoCard* videocard, Memory* memory) {
		m_cpu = cpu;
		m_videocard = videocard;
		m_memory = memory;
	}
	//工作函数:让零件调用起来的工作接口  父类指针调用接口时就已经是多态技术了
	void DoWork() {
		//Cpu进行计算操作
		m_cpu->Calculate();
		//显卡进行显示操作
		m_videocard->Display();
		//内存条进行存储操作
		m_memory->Storage();
	}
	//提供析构函数释放电脑的三个零件
	~Computer() {
		if (m_cpu != NULL) {
			delete m_cpu;
			m_cpu = NULL;
		}
		if (m_videocard != NULL) {
			delete m_videocard;
			m_videocard = NULL;
		}
		if (m_memory != NULL) {
			delete m_memory;
			m_memory = NULL;
		}
	}
private:
	Cpu *m_cpu;
	VideoCard *m_videocard;
	Memory *m_memory;
};


//具体厂商///
//因特尔厂商
class IntelCpu :public Cpu{
public:
	//子类重写父类的虚函数
	virtual void Calculate() {
		cout << "Intel的Cpu开始计算了！" << endl;
	}
	/*~IntelCpu() {
		cout << "这是子类IntelCpu的析构函数调用" << endl;
	}*/
};
class IntelVideoCard :public VideoCard {
public:
	//子类重写父类的虚函数
	virtual void Display() {
		cout << "Intel的显卡开始显示屏幕了！" << endl;
	}
};
class IntelMemory :public Memory {
public:
	//子类重写父类的虚函数
	virtual void Storage() {
		cout << "Intel的内存条开始存储数据了！" << endl;
	}
};

//Lenovo厂商
class LenovoCpu :public Cpu {
public:
	//子类重写父类的虚函数
	virtual void Calculate() {
		cout << "Lenovo的Cpu开始计算了！" << endl;
	}
};
class LenovoVideoCard :public VideoCard {
public:
	//子类重写父类的虚函数
	virtual void Display() {
		cout << "Lenovo的显卡开始显示屏幕了！" << endl;
	}
};
class LenovoMemory :public Memory {
public:
	//子类重写父类的虚函数
	virtual void Storage() {
		cout << "Lenovo的内存条开始存储数据了！" << endl;
	}
};


//开始测试，组装不同的电脑
void test01() {
	//第一台电脑的零件
	//父类指针指向了子类对象，利用了多态技术
	Cpu* intelcpu = new IntelCpu;
	VideoCard* intelvideocard = new IntelVideoCard;
	Memory* intelmemory = new IntelMemory;
	//创建第一台电脑
	cout << "组装好的第一台电脑配置如下：" << endl;
	Computer* computer1 = new Computer(intelcpu,intelvideocard,intelmemory);
	computer1->DoWork();
	delete computer1;

	//创建第二台电脑
	cout << "组装好的第二台电脑配置如下：" << endl;
	Computer* computer2 = new Computer(new LenovoCpu, new LenovoVideoCard, new LenovoMemory);
	computer2->DoWork();
	delete computer2;

	//创建第三台电脑
	cout << "组装好的第三台电脑配置如下：" << endl;
	Computer* computer3 = new Computer(new LenovoCpu, new IntelVideoCard, new LenovoMemory);
	computer3->DoWork();
	delete computer3;

}

int main() {
	test01();
	system("pause");
	return 0;
}