c++-純虛函式和抽象類

純虛函式和抽象類

• C面向介面編程和C多型
  • 函式型別語法基礎
  • 函式指標做函式引數(回呼函式)思想剖析
  • 函式指標做函式引數兩種用法（正向呼叫、反向呼叫）
• 純虛函式 抽象類
  • 抽象類基本概念
  • 抽象類在多繼承中的應用
  • 面向抽象類編程案例強化
  • C面向介面編程和C多型

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>


using namespace std;


//圖形類
//如果說一個類 擁有一個純虛函式 
//就稱這個類是一個抽象類，
//不管這個類中有沒有成員屬性，只要這個類有純虛函式，就是一個抽象類， 抽象類就是不能夠實體化的，
class Shape
{
public:
	//求圖形面積的方法
	//表示圖形類宣告一個方法getArea（），它是一個純虛函式，沒有函式的實作，
	virtual double getArea() = 0;
};

//三角形
class Tri :public Shape
{
public:
	Tri(int a, int h)
	{
		this->a = a;
		this->h = h;
	}
	virtual double getArea() {
		cout << "三角形求面價" << endl;
		return 0.5*a*h;
	}

private:
	int a;
	int h;
};

//正方形：
//如果說一個普通類，繼承擁有純虛函式的類，如果說不重寫純虛函式，依然是一個抽象類，
//依然不能被實體化， 如果想實體化， 必須要重寫這個父類中所有純虛函式
class Rect : public Shape
{
public:
	Rect(int a) {
		this->a = a;
	}
	virtual double getArea() {
		cout << "正方形求面積" << endl;
		return a*a;
	}
private:
	int a;//正方形邊長
};

class Circle :public Shape
{
public:
	Circle(int r)
	{
		this->r = r;
	}

	virtual double getArea()
	{
		cout << "圓形求面積" << endl;

		return 3.14*r * 4;
	}


private:
	int  r;
};


//面向抽象類寫一個架構函式
void printArea(Shape *sp)
{
	sp->getArea();
}

//業務層  面向的抽象類編程
int main(void)
{
	//main 中所有使用的變數型別 都是 抽象類Shape的型別，
	Shape *sp1 = new Rect(10);
	//sp1->getArea();

	Shape *sp2 = new Circle(20);
	//sp2->getArea();

	Shape *sp3 = new Tri(10, 20);
	//sp3->getArea();


	printArea(sp1);
	printArea(sp2);
	printArea(sp3);

	return 0;
}

上一個知識的小練習

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>


using namespace std;

//大哥的虛銜
class BigBrother
{
public:
	//會打人，
	virtual void fightPeople() = 0;
};

//東方不敗
class EastNeverLose :public BigBrother
{
public:
	virtual void fightPeople()  {
		cout << "使用了葵花寶典區打人" << endl;
	}
};

//無崖子
class Wuyazi :public BigBrother
{
public:
	virtual void fightPeople()  {
		cout << "使用北冥神功打人" << endl;
	}
};



//boss
int main(void)
{
	BigBrother *bigbrother = new Wuyazi;

	//大哥你給我去打人，
	bigbrother->fightPeople();

	delete bigbrother;
	
	return 0;
}

純虛函式和多繼承

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>


using namespace std;

//介面1
class Interface1
{
public:
	virtual void func1(int a, int b) = 0;
	virtual void func3(int a, int b) = 0;
};


//介面2
class Interface2
{
public:
	virtual void func2(int a) = 0;
};

class Child :public Interface1, public Interface2
{
public:
	virtual void func1(int a, int b)
	{
		cout << "func1" << endl;
	}
	virtual void func3(int a, int b) {
		cout << "func3" << endl;

	}


	virtual void func2(int a)
	{
		cout << "func2 " << endl;
	}
};

int main(void)
{
	Interface1 *if1 = new Child;

	if1->func1(10, 20);
	if1->func3(100, 200);


	Interface2 *if2 = new Child;

	if2->func2(10);

	return 0;
}

電腦組裝--小練習

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>


using namespace std;

//--------  抽象層---------
//抽象CPU類
class CPU
{
public:
	CPU();
	virtual void caculate() = 0;
};

//抽象的card類
class Card
{
public:
	virtual void display() = 0;
};

//抽象的記憶體類
class Memory
{
public:
	virtual void storage() = 0;
};

//架構類
class Computer
{
public:
	Computer(CPU *cpu, Card *card, Memory *mem)
	{
		this->cpu = cpu;
		this->card = card;
		this->mem = mem;
	}

	void work()
	{
		this->cpu->caculate();
		this->card->display();
		this->mem->storage();
	}

	~Computer() {
		if (this->cpu != NULL) {
			delete this->cpu;
		}
		if (this->card != NULL) {
			delete this->card;
		}
		if (this->mem != NULL) {
			delete this->mem;
		}
	}
private:
	CPU* cpu;
	Card*card;
	Memory *mem;
};
// --------------------------

//-----------實作層----------
//具體的IntelCPU
class IntelCPU :public CPU
{
public:
	virtual void caculate() {
		cout << "Intel CPU開始計算了" << endl;
	}
};

class IntelCard :public Card
{
public:
	virtual void display() {
		cout << "Intel Card開始顯示了" << endl;

	}
};

class IntelMem :public Memory {
public:
	virtual void storage() {
		cout << "Intel mem開始存盤了" << endl;

	}
};

class NvidiaCard :public Card
{
public:
	virtual void display() {
		cout << "Nvidia 顯卡開始顯示了" << endl;
	}
};

class KingstonMem :public Memory {
public:
	virtual void storage() {
		cout << "KingstonMem 開始存盤了" << endl;
	}
};

//--------------------------



//--------業務層-------------------
int main(void)
{
	//1 組裝第一臺intel系列的電腦
#if 0
	CPU *intelCpu = new IntelCPU;
	Card *intelCard = new IntelCard;
	Memory *intelMem = new IntelMem;

	Computer *com1 = new Computer(intelCpu, intelCard, intelMem);

	com1->work();

	Card *nCard = new NvidiaCard;
	Memory* kMem = new KingstonMem;

	Computer *com2 = new Computer(intelCpu, nCard, kMem);

	com2->work();

	delete intelCpu;
#endif
	Computer *com1 = new Computer(new IntelCPU, new IntelCard, new IntelMem);
	com1->work();
	delete com1;


	return 0;
}

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