C++ 【第二篇】面向对象编程（一）

面向对象编程

一对象的初始化和清理

class Person
{
public:
    //构造函数
    Person()
    {
        cout << "Person的构造函数调用" << endl;
    }
    //析构函数
    ~Person()
    {
        cout << "Person的析构函数调用" << endl;
    }

};

void test01()
{
    Person p;
}

int main() {
    
    test01();

    system("pause");

    return 0;
}

1构造与析构

//1、构造函数分类
// 按照参数分类分为 有参和无参构造   无参又称为默认构造函数
// 按照类型分类分为 普通构造和拷贝构造

class Person {
public:
    //无参（默认）构造函数
    Person() {
        cout << "无参构造函数!" << endl;
    }
    //有参构造函数
    Person(int a) {
        age = a;
        cout << "有参构造函数!" << endl;
    }
    //拷贝构造函数
    Person(const Person& p) {
        age = p.age;
        cout << "拷贝构造函数!" << endl;
    }
    //析构函数
    ~Person() {
        cout << "析构函数!" << endl;
    }
public:
    int age;
};

//2、构造函数的调用
//调用无参构造函数
void test01() {
    Person p; //调用无参构造函数
}

//调用有参的构造函数
void test02() {

    //2.1  括号法，常用
    Person p1(10);
    //注意1：调用无参构造函数不能加括号，如果加了编译器认为这是一个函数声明
    //Person p2();

    //2.2 显式法
    Person p2 = Person(10); 
    Person p3 = Person(p2);
    //Person(10)单独写就是匿名对象  当前行结束之后，马上析构

    //2.3 隐式转换法
    Person p4 = 10; // Person p4 = Person(10); 
    Person p5 = p4; // Person p5 = Person(p4); 

    //注意2：不能利用 拷贝构造函数 初始化匿名对象 编译器认为是对象声明
    //Person p5(p4);
}

int main() {

    test01();
    //test02();

    system("pause");

    return 0;
}

构造函数分类

class Person {
public:
    Person() {
        cout << "无参构造函数!" << endl;
        mAge = 0;
    }
    Person(int age) {
        cout << "有参构造函数!" << endl;
        mAge = age;
    }
    Person(const Person& p) {
        cout << "拷贝构造函数!" << endl;
        mAge = p.mAge;
    }
    //析构函数在释放内存之前调用
    ~Person() {
        cout << "析构函数!" << endl;
    }
public:
    int mAge;
};

//1. 使用一个已经创建完毕的对象来初始化一个新对象
void test01() {

    Person man(100); //p对象已经创建完毕
    Person newman(man); //调用拷贝构造函数
    Person newman2 = man; //拷贝构造

    //Person newman3;
    //newman3 = man; //不是调用拷贝构造函数，赋值操作
}

//2. 值传递的方式给函数参数传值
//相当于Person p1 = p;
void doWork(Person p1) {}
void test02() {
    Person p; //无参构造函数
    doWork(p);
}

//3. 以值方式返回局部对象
Person doWork2()
{
    Person p1;
    cout << (int *)&p1 << endl;
    return p1;
}

void test03()
{
    Person p = doWork2();
    cout << (int *)&p << endl;
}


int main() {

    //test01();
    //test02();
    test03();

    system("pause");

    return 0;
}

拷贝构造函数

class Person {
public:
    //无参（默认）构造函数
    Person() {
        cout << "无参构造函数!" << endl;
    }
    //有参构造函数
    Person(int age ,int height) {
        
        cout << "有参构造函数!" << endl;

        m_age = age;
        m_height = new int(height);
        
    }
    //拷贝构造函数  
    Person(const Person& p) {
        cout << "拷贝构造函数!" << endl;
        //如果不利用深拷贝在堆区创建新内存，会导致浅拷贝带来的重复释放堆区问题
        m_age = p.m_age;
        m_height = new int(*p.m_height);
        
    }

    //析构函数
    ~Person() {
        cout << "析构函数!" << endl;
        if (m_height != NULL)
        {
            delete m_height;
        }
    }
public:
    int m_age;
    int* m_height;
};

void test01()
{
    Person p1(18, 180);

    Person p2(p1);

    cout << "p1的年龄： " << p1.m_age << " 身高： " << *p1.m_height << endl;

    cout << "p2的年龄： " << p2.m_age << " 身高： " << *p2.m_height << endl;
}

int main() {

    test01();

    system("pause");

    return 0;
}

深浅copy

class Person {
public:

    ////传统方式初始化
    //Person(int a, int b, int c) {
    //    m_A = a;
    //    m_B = b;
    //    m_C = c;
    //}

    //初始化列表方式初始化
    Person(int a, int b, int c) :m_A(a), m_B(b), m_C(c) {}
    void PrintPerson() {
        cout << "mA:" << m_A << endl;
        cout << "mB:" << m_B << endl;
        cout << "mC:" << m_C << endl;
    }
private:
    int m_A;
    int m_B;
    int m_C;
};

int main() {

    Person p(1, 2, 3);
    p.PrintPerson();


    system("pause");

    return 0;
}

初始化列表

class Person {
public:

    ////传统方式初始化
    //Person(int a, int b, int c) {
    //    m_A = a;
    //    m_B = b;
    //    m_C = c;
    //}

    //初始化列表方式初始化
    Person(int a, int b, int c) :m_A(a), m_B(b), m_C(c) {}
    void PrintPerson() {
        cout << "mA:" << m_A << endl;
        cout << "mB:" << m_B << endl;
        cout << "mC:" << m_C << endl;
    }
private:
    int m_A;
    int m_B;
    int m_C;
};

int main() {

    Person p(1, 2, 3);
    p.PrintPerson();


    system("pause");

    return 0;
}

类对象作为类成员

class Person
{
    
public:

    static int m_A; //静态成员变量

    //静态成员变量特点：
    //1 在编译阶段分配内存
    //2 类内声明，类外初始化
    //3 所有对象共享同一份数据

private:
    static int m_B; //静态成员变量也是有访问权限的
};
int Person::m_A = 10;
int Person::m_B = 10;

void test01()
{
    //静态成员变量两种访问方式

    //1、通过对象
    Person p1;
    p1.m_A = 100;
    cout << "p1.m_A = " << p1.m_A << endl;

    Person p2;
    p2.m_A = 200;
    cout << "p1.m_A = " << p1.m_A << endl; //共享同一份数据
    cout << "p2.m_A = " << p2.m_A << endl;

    //2、通过类名
    cout << "m_A = " << Person::m_A << endl;


    //cout << "m_B = " << Person::m_B << endl; //私有权限访问不到
}

int main() {

    test01();

    system("pause");

    return 0;
}

静态成员变量

class Person
{

public:

    //静态成员函数特点：
    //1 程序共享一个函数
    //2 静态成员函数只能访问静态成员变量
    
    static void func()
    {
        cout << "func调用" << endl;
        m_A = 100;
        //m_B = 100; //错误，不可以访问非静态成员变量
    }

    static int m_A; //静态成员变量
    int m_B; // 
private:

    //静态成员函数也是有访问权限的
    static void func2()
    {
        cout << "func2调用" << endl;
    }
};
int Person::m_A = 10;


void test01()
{
    //静态成员变量两种访问方式

    //1、通过对象
    Person p1;
    p1.func();

    //2、通过类名
    Person::func();


    //Person::func2(); //私有权限访问不到
}

int main() {

    test01();

    system("pause");

    return 0;
}

静态成员函数

二对象模型与this指针

class Person {
public:
    Person() {
        mA = 0;
    }
    //非静态成员变量占对象空间
    int mA;
    //静态成员变量不占对象空间
    static int mB; 
    //函数也不占对象空间，所有函数共享一个函数实例
    void func() {
        cout << "mA:" << this->mA << endl;
    }
    //静态成员函数也不占对象空间
    static void sfunc() {
    }
};

int main() {

    cout << sizeof(Person) << endl;

    system("pause");

    return 0;
}

成员变量与成员函数分开存储

class Person
{
public:

    Person(int age)
    {
        //1、当形参和成员变量同名时，可用this指针来区分
        this->age = age;
    }

    Person& PersonAddPerson(Person p)
    {
        this->age += p.age;
        //返回对象本身
        return *this;
    }

    int age;
};

void test01()
{
    Person p1(10);
    cout << "p1.age = " << p1.age << endl;

    Person p2(10);
    p2.PersonAddPerson(p1).PersonAddPerson(p1).PersonAddPerson(p1);
    cout << "p2.age = " << p2.age << endl;
}

int main() {

    test01();

    system("pause");

    return 0;
}

this指针

//空指针访问成员函数
class Person {
public:

    void ShowClassName() {
        cout << "我是Person类!" << endl;
    }

    void ShowPerson() {
        if (this == NULL) {
            return;
        }
        cout << mAge << endl;
    }

public:
    int mAge;
};

void test01()
{
    Person * p = NULL;
    p->ShowClassName(); //空指针，可以调用成员函数
    p->ShowPerson();  //但是如果成员函数中用到了this指针，就不可以了
}

int main() {

    test01();

    system("pause");

    return 0;
}

空指针访问成员函数

class Person {
public:
    Person() {
        m_A = 0;
        m_B = 0;
    }

    //this指针的本质是一个指针常量，指针的指向不可修改
    //如果想让指针指向的值也不可以修改，需要声明常函数
    void ShowPerson() const {
        //const Type* const pointer;
        //this = NULL; //不能修改指针的指向 Person* const this;
        //this->mA = 100; //但是this指针指向的对象的数据是可以修改的

        //const修饰成员函数，表示指针指向的内存空间的数据不能修改，除了mutable修饰的变量
        this->m_B = 100;
    }

    void MyFunc() const {
        //mA = 10000;
    }

public:
    int m_A;
    mutable int m_B; //可修改 可变的
};


//const修饰对象  常对象
void test01() {

    const Person person; //常量对象  
    cout << person.m_A << endl;
    //person.mA = 100; //常对象不能修改成员变量的值,但是可以访问
    person.m_B = 100; //但是常对象可以修改mutable修饰成员变量

    //常对象访问成员函数
    person.MyFunc(); //常对象不能调用const的函数

}

int main() {

    test01();

    system("pause");

    return 0;
}

const修饰成员函数

三友元

友元的目的就是让一个函数或者类访问另一个类中私有成员

class Building
{
    //告诉编译器 goodGay全局函数 是 Building类的好朋友，可以访问类中的私有内容
    friend void goodGay(Building * building);

public:

    Building()
    {
        this->m_SittingRoom = "客厅";
        this->m_BedRoom = "卧室";
    }


public:
    string m_SittingRoom; //客厅

private:
    string m_BedRoom; //卧室
};


void goodGay(Building * building)
{
    cout << "好基友正在访问： " << building->m_SittingRoom << endl;
    cout << "好基友正在访问： " << building->m_BedRoom << endl;
}


void test01()
{
    Building b;
    goodGay(&b);
}

int main(){

    test01();

    system("pause");
    return 0;
}

全局函数作友元

class Building;
class goodGay
{
public:

    goodGay();
    void visit();

private:
    Building *building;
};


class Building
{
    //告诉编译器 goodGay类是Building类的好朋友，可以访问到Building类中私有内容
    friend class goodGay;

public:
    Building();

public:
    string m_SittingRoom; //客厅
private:
    string m_BedRoom;//卧室
};

Building::Building()
{
    this->m_SittingRoom = "客厅";
    this->m_BedRoom = "卧室";
}

goodGay::goodGay()
{
    building = new Building;
}

void goodGay::visit()
{
    cout << "好基友正在访问" << building->m_SittingRoom << endl;
    cout << "好基友正在访问" << building->m_BedRoom << endl;
}

void test01()
{
    goodGay gg;
    gg.visit();

}

int main(){

    test01();

    system("pause");
    return 0;
}

类做友元

class Building;
class goodGay
{
public:

    goodGay();
    void visit(); //只让visit函数作为Building的好朋友，可以发访问Building中私有内容
    void visit2(); 

private:
    Building *building;
};


class Building
{
    //告诉编译器  goodGay类中的visit成员函数 是Building好朋友，可以访问私有内容
    friend void goodGay::visit();

public:
    Building();

public:
    string m_SittingRoom; //客厅
private:
    string m_BedRoom;//卧室
};

Building::Building()
{
    this->m_SittingRoom = "客厅";
    this->m_BedRoom = "卧室";
}

goodGay::goodGay()
{
    building = new Building;
}

void goodGay::visit()
{
    cout << "好基友正在访问" << building->m_SittingRoom << endl;
    cout << "好基友正在访问" << building->m_BedRoom << endl;
}

void goodGay::visit2()
{
    cout << "好基友正在访问" << building->m_SittingRoom << endl;
    //cout << "好基友正在访问" << building->m_BedRoom << endl;
}

void test01()
{
    goodGay  gg;
    gg.visit();

}

int main(){
    
    test01();

    system("pause");
    return 0;
}

成员函数作友元

四运算符重载

class Person {
public:
    Person() {};
    Person(int a, int b)
    {
        this->m_A = a;
        this->m_B = b;
    }
    //成员函数实现 + 号运算符重载
    Person operator+(const Person& p) {
        Person temp;
        temp.m_A = this->m_A + p.m_A;
        temp.m_B = this->m_B + p.m_B;
        return temp;
    }


public:
    int m_A;
    int m_B;
};

//全局函数实现 + 号运算符重载
//Person operator+(const Person& p1, const Person& p2) {
//    Person temp(0, 0);
//    temp.m_A = p1.m_A + p2.m_A;
//    temp.m_B = p1.m_B + p2.m_B;
//    return temp;
//}

//运算符重载 可以发生函数重载 
Person operator+(const Person& p2, int val)  
{
    Person temp;
    temp.m_A = p2.m_A + val;
    temp.m_B = p2.m_B + val;
    return temp;
}

void test() {

    Person p1(10, 10);
    Person p2(20, 20);

    //成员函数方式
    Person p3 = p2 + p1;  //相当于 p2.operaor+(p1)
    cout << "mA:" << p3.m_A << " mB:" << p3.m_B << endl;


    Person p4 = p3 + 10; //相当于 operator+(p3,10)
    cout << "mA:" << p4.m_A << " mB:" << p4.m_B << endl;

}

int main() {

    test();

    system("pause");

    return 0;
}

加号运算符重载

class Person {
    friend ostream& operator<<(ostream& out, Person& p);

public:

    Person(int a, int b)
    {
        this->m_A = a;
        this->m_B = b;
    }

    //成员函数 实现不了  p << cout 不是我们想要的效果
    //void operator<<(Person& p){
    //}

private:
    int m_A;
    int m_B;
};

//全局函数实现左移重载
//ostream对象只能有一个
ostream& operator<<(ostream& out, Person& p) {
    out << "a:" << p.m_A << " b:" << p.m_B;
    return out;
}

void test() {

    Person p1(10, 20);

    cout << p1 << "hello world" << endl; //链式编程
}

int main() {

    test();

    system("pause");

    return 0;
}

左移运算符重载

class MyInteger {

    friend ostream& operator<<(ostream& out, MyInteger myint);

public:
    MyInteger() {
        m_Num = 0;
    }
    //前置++
    MyInteger& operator++() {
        //先++
        m_Num++;
        //再返回
        return *this;
    }

    //后置++
    MyInteger operator++(int) {
        //先返回
        MyInteger temp = *this; //记录当前本身的值，然后让本身的值加1，但是返回的是以前的值，达到先返回后++；
        m_Num++;
        return temp;
    }

private:
    int m_Num;
};


ostream& operator<<(ostream& out, MyInteger myint) {
    out << myint.m_Num;
    return out;
}


//前置++ 先++ 再返回
void test01() {
    MyInteger myInt;
    cout << ++myInt << endl;
    cout << myInt << endl;
}

//后置++ 先返回 再++
void test02() {

    MyInteger myInt;
    cout << myInt++ << endl;
    cout << myInt << endl;
}

int main() {

    test01();
    //test02();

    system("pause");

    return 0;
}

递增运算符重载

class Person
{
public:

    Person(int age)
    {
        //将年龄数据开辟到堆区
        m_Age = new int(age);
    }

    //重载赋值运算符 
    Person& operator=(Person &p)
    {
        if (m_Age != NULL)
        {
            delete m_Age;
            m_Age = NULL;
        }
        //编译器提供的代码是浅拷贝
        //m_Age = p.m_Age;

        //提供深拷贝 解决浅拷贝的问题
        m_Age = new int(*p.m_Age);

        //返回自身
        return *this;
    }


    ~Person()
    {
        if (m_Age != NULL)
        {
            delete m_Age;
            m_Age = NULL;
        }
    }

    //年龄的指针
    int *m_Age;

};


void test01()
{
    Person p1(18);

    Person p2(20);

    Person p3(30);

    p3 = p2 = p1; //赋值操作

    cout << "p1的年龄为：" << *p1.m_Age << endl;

    cout << "p2的年龄为：" << *p2.m_Age << endl;

    cout << "p3的年龄为：" << *p3.m_Age << endl;
}

int main() {

    test01();

    //int a = 10;
    //int b = 20;
    //int c = 30;

    //c = b = a;
    //cout << "a = " << a << endl;
    //cout << "b = " << b << endl;
    //cout << "c = " << c << endl;

    system("pause");

    return 0;
}

赋值运算符重载

class Person
{
public:
    Person(string name, int age)
    {
        this->m_Name = name;
        this->m_Age = age;
    };

    bool operator==(Person & p)
    {
        if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    bool operator!=(Person & p)
    {
        if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    string m_Name;
    int m_Age;
};

void test01()
{
    //int a = 0;
    //int b = 0;

    Person a("孙悟空", 18);
    Person b("孙悟空", 18);

    if (a == b)
    {
        cout << "a和b相等" << endl;
    }
    else
    {
        cout << "a和b不相等" << endl;
    }

    if (a != b)
    {
        cout << "a和b不相等" << endl;
    }
    else
    {
        cout << "a和b相等" << endl;
    }
}


int main() {

    test01();

    system("pause");

    return 0;
}

关系运算符重载

class MyPrint
{
public:
    void operator()(string text)
    {
        cout << text << endl;
    }

};
void test01()
{
    //重载的（）操作符 也称为仿函数
    MyPrint myFunc;
    myFunc("hello world");
}


class MyAdd
{
public:
    int operator()(int v1, int v2)
    {
        return v1 + v2;
    }
};

void test02()
{
    MyAdd add;
    int ret = add(10, 10);
    cout << "ret = " << ret << endl;

    //匿名对象调用  
    cout << "MyAdd()(100,100) = " << MyAdd()(100, 100) << endl;
}

int main() {

    test01();
    test02();

    system("pause");

    return 0;
}

函数调用运算符重载

五封装

C++中 struct和class唯一的区别就在于 默认的访问权限不同

truct 默认权限为公共
class 默认权限为私有

class C1
{
    int  m_A; //默认是私有权限
};

struct C2
{
    int m_A;  //默认是公共权限
};

int main() {

    C1 c1;
    c1.m_A = 10; //错误，访问权限是私有

    C2 c2;
    c2.m_A = 10; //正确，访问权限是公共

    system("pause");

    return 0;
}

View Code

//圆周率
const double PI = 3.14;

//1、封装的意义
//将属性和行为作为一个整体，用来表现生活中的事物

//封装一个圆类，求圆的周长
//class代表设计一个类，后面跟着的是类名
class Circle
{
public:  //访问权限  公共的权限

    //属性
    int m_r;//半径

    //行为
    //获取到圆的周长
    double calculateZC()
    {
        //2 * pi  * r
        //获取圆的周长
        return  2 * PI * m_r;
    }
};

int main() {

    //通过圆类，创建圆的对象
    // c1就是一个具体的圆
    Circle c1;
    c1.m_r = 10; //给圆对象的半径 进行赋值操作

    //2 * pi * 10 = = 62.8
    cout << "圆的周长为： " << c1.calculateZC() << endl;

    system("pause");

    return 0;
}

1封装基础

//学生类
class Student {
public:
    void setName(string name) {
        m_name = name;
    }
    void setID(int id) {
        m_id = id;
    }

    void showStudent() {
        cout << "name:" << m_name << " ID:" << m_id << endl;
    }
public:
    string m_name;
    int m_id;
};

int main() {

    Student stu;
    stu.setName("德玛西亚");
    stu.setID(250);
    stu.showStudent();

    system("pause");

    return 0;
}

2 示例二

//三种权限
//公共权限  public     类内可以访问  类外可以访问
//保护权限  protected  类内可以访问  类外不可以访问
//私有权限  private    类内可以访问  类外不可以访问

class Person
{
    //姓名  公共权限
public:
    string m_Name;

    //汽车  保护权限
protected:
    string m_Car;

    //银行卡密码  私有权限
private:
    int m_Password;

public:
    void func()
    {
        m_Name = "张三";
        m_Car = "拖拉机";
        m_Password = 123456;
    }
};

int main() {

    Person p;
    p.m_Name = "李四";
    //p.m_Car = "奔驰";  //保护权限类外访问不到
    //p.m_Password = 123; //私有权限类外访问不到

    system("pause");

    return 0;
}

3 三种权限

class Person {
public:

    //姓名设置可读可写
    void setName(string name) {
        m_Name = name;
    }
    string getName()
    {
        return m_Name;
    }


    //获取年龄 
    int getAge() {
        return m_Age;
    }
    //设置年龄
    void setAge(int age) {
        if (age < 0 || age > 150) {
            cout << "你个老妖精!" << endl;
            return;
        }
        m_Age = age;
    }

    //情人设置为只写
    void setLover(string lover) {
        m_Lover = lover;
    }

private:
    string m_Name; //可读可写  姓名
    
    int m_Age; //只读  年龄

    string m_Lover; //只写  情人
};


int main() {

    Person p;
    //姓名设置
    p.setName("张三");
    cout << "姓名： " << p.getName() << endl;

    //年龄设置
    p.setAge(50);
    cout << "年龄： " << p.getAge() << endl;

    //情人设置
    p.setLover("苍井");
    //cout << "情人： " << p.m_Lover << endl;  //只写属性，不可以读取

    system("pause");

    return 0;
}

4设为私有属性

六继承

//公共页面
class BasePage
{
public:
    void header()
    {
        cout << "首页、公开课、登录、注册...（公共头部）" << endl;
    }

    void footer()
    {
        cout << "帮助中心、交流合作、站内地图...(公共底部)" << endl;
    }
    void left()
    {
        cout << "Java,Python,C++...(公共分类列表)" << endl;
    }

};

//Java页面
class Java : public BasePage
{
public:
    void content()
    {
        cout << "JAVA学科视频" << endl;
    }
};
//Python页面
class Python : public BasePage
{
public:
    void content()
    {
        cout << "Python学科视频" << endl;
    }
};
//C++页面
class CPP : public BasePage
{
public:
    void content()
    {
        cout << "C++学科视频" << endl;
    }
};

void test01()
{
    //Java页面
    cout << "Java下载视频页面如下： " << endl;
    Java ja;
    ja.header();
    ja.footer();
    ja.left();
    ja.content();
    cout << "--------------------" << endl;

    //Python页面
    cout << "Python下载视频页面如下： " << endl;
    Python py;
    py.header();
    py.footer();
    py.left();
    py.content();
    cout << "--------------------" << endl;

    //C++页面
    cout << "C++下载视频页面如下： " << endl;
    CPP cp;
    cp.header();
    cp.footer();
    cp.left();
    cp.content();


}

int main() {

    test01();

    system("pause");

    return 0;
}

1简单实现

class Base1
{
public: 
    int m_A;
protected:
    int m_B;
private:
    int m_C;
};

//公共继承
class Son1 :public Base1
{
public:
    void func()
    {
        m_A; //可访问 public权限
        m_B; //可访问 protected权限
        //m_C; //不可访问
    }
};

void myClass()
{
    Son1 s1;
    s1.m_A; //其他类只能访问到公共权限
}

//保护继承
class Base2
{
public:
    int m_A;
protected:
    int m_B;
private:
    int m_C;
};
class Son2:protected Base2
{
public:
    void func()
    {
        m_A; //可访问 protected权限
        m_B; //可访问 protected权限
        //m_C; //不可访问
    }
};
void myClass2()
{
    Son2 s;
    //s.m_A; //不可访问
}

//私有继承
class Base3
{
public:
    int m_A;
protected:
    int m_B;
private:
    int m_C;
};
class Son3:private Base3
{
public:
    void func()
    {
        m_A; //可访问 private权限
        m_B; //可访问 private权限
        //m_C; //不可访问
    }
};
class GrandSon3 :public Son3
{
public:
    void func()
    {
        //Son3是私有继承，所以继承Son3的属性在GrandSon3中都无法访问到
        //m_A;
        //m_B;
        //m_C;
    }
};

2继承的三种方式

class Base 
{
public:
    Base()
    {
        cout << "Base构造函数!" << endl;
    }
    ~Base()
    {
        cout << "Base析构函数!" << endl;
    }
};

class Son : public Base
{
public:
    Son()
    {
        cout << "Son构造函数!" << endl;
    }
    ~Son()
    {
        cout << "Son析构函数!" << endl;
    }

};


void test01()
{
    //继承中 先调用父类构造函数，再调用子类构造函数，析构顺序与构造相反
    Son s;
}

int main() {

    test01();

    system("pause");

    return 0;
}

3继承构造与析构顺序

总结：
1. 子类对象可以直接访问到子类中同名成员
2. 子类对象加作用域可以访问到父类同名成员
3. 当子类与父类拥有同名的成员函数，子类会隐藏父类中同名成员函数，加作用域可以访问到父类中同名函数


class Base {
public:
    Base()
    {
        m_A = 100;
    }

    void func()
    {
        cout << "Base - func()调用" << endl;
    }

    void func(int a)
    {
        cout << "Base - func(int a)调用" << endl;
    }

public:
    int m_A;
};


class Son : public Base {
public:
    Son()
    {
        m_A = 200;
    }

    //当子类与父类拥有同名的成员函数，子类会隐藏父类中所有版本的同名成员函数
    //如果想访问父类中被隐藏的同名成员函数，需要加父类的作用域
    void func()
    {
        cout << "Son - func()调用" << endl;
    }
public:
    int m_A;
};

void test01()
{
    Son s;

    cout << "Son下的m_A = " << s.m_A << endl;
    cout << "Base下的m_A = " << s.Base::m_A << endl;

    s.func();
    s.Base::func();
    s.Base::func(10);

}
int main() {

    test01();

    system("pause");
    return EXIT_SUCCESS;
}

4继承同名成员处理方式

//总结：同名静态成员处理方式和非静态处理方式一样，只不过有两种访问的方式（通过对象 和 通过类名）

class Base {
public:
    static void func()
    {
        cout << "Base - static void func()" << endl;
    }
    static void func(int a)
    {
        cout << "Base - static void func(int a)" << endl;
    }

    static int m_A;
};

int Base::m_A = 100;

class Son : public Base {
public:
    static void func()
    {
        cout << "Son - static void func()" << endl;
    }
    static int m_A;
};

int Son::m_A = 200;

//同名成员属性
void test01()
{
    //通过对象访问
    cout << "通过对象访问： " << endl;
    Son s;
    cout << "Son  下 m_A = " << s.m_A << endl;
    cout << "Base 下 m_A = " << s.Base::m_A << endl;

    //通过类名访问
    cout << "通过类名访问： " << endl;
    cout << "Son  下 m_A = " << Son::m_A << endl;
    cout << "Base 下 m_A = " << Son::Base::m_A << endl;
}

//同名成员函数
void test02()
{
    //通过对象访问
    cout << "通过对象访问： " << endl;
    Son s;
    s.func();
    s.Base::func();

    cout << "通过类名访问： " << endl;
    Son::func();
    Son::Base::func();
    //出现同名，子类会隐藏掉父类中所有同名成员函数，需要加作作用域访问
    Son::Base::func(100);
}
int main() {

    //test01();
    test02();

    system("pause");

    return 0;
}

5继承同名静态成员处理方式

class Base1 {
public:
    Base1()
    {
        m_A = 100;
    }
public:
    int m_A;
};

class Base2 {
public:
    Base2()
    {
        m_A = 200;  //开始是m_B 不会出问题，但是改为mA就会出现不明确
    }
public:
    int m_A;
};

//语法：class 子类：继承方式 父类1 ，继承方式 父类2 
class Son : public Base2, public Base1 
{
public:
    Son()
    {
        m_C = 300;
        m_D = 400;
    }
public:
    int m_C;
    int m_D;
};


//多继承容易产生成员同名的情况
//通过使用类名作用域可以区分调用哪一个基类的成员
void test01()
{
    Son s;
    cout << "sizeof Son = " << sizeof(s) << endl;
    cout << s.Base1::m_A << endl;
    cout << s.Base2::m_A << endl;
}

int main() {

    test01();

    system("pause");

    return 0;
}

6多继承（不建议使用）

七多态

class Animal
{
public:
    //Speak函数就是虚函数
    //函数前面加上virtual关键字，变成虚函数，那么编译器在编译的时候就不能确定函数调用了。
    virtual void speak()
    {
        cout << "动物在说话" << endl;
    }
};

class Cat :public Animal
{
public:
    void speak()
    {
        cout << "小猫在说话" << endl;
    }
};

class Dog :public Animal
{
public:

    void speak()
    {
        cout << "小狗在说话" << endl;
    }

};
//我们希望传入什么对象，那么就调用什么对象的函数
//如果函数地址在编译阶段就能确定，那么静态联编
//如果函数地址在运行阶段才能确定，就是动态联编

void DoSpeak(Animal & animal)
{
    animal.speak();
}
//
//多态满足条件： 
//1、有继承关系
//2、子类重写父类中的虚函数
//多态使用：
//父类指针或引用指向子类对象

void test01()
{
    Cat cat;
    DoSpeak(cat);


    Dog dog;
    DoSpeak(dog);
}


int main() {

    test01();

    system("pause");

    return 0;
}

1多态示例

//普通实现
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;
        }
        //如果要提供新的运算，需要修改源码
    }
public:
    int m_Num1;
    int m_Num2;
};

void test01()
{
    //普通实现测试
    Calculator c;
    c.m_Num1 = 10;
    c.m_Num2 = 10;
    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;
}



//多态实现
//抽象计算器类
//多态优点：代码组织结构清晰，可读性强，利于前期和后期的扩展以及维护
class AbstractCalculator
{
public :

    virtual int getResult()
    {
        return 0;
    }

    int m_Num1;
    int m_Num2;
};

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

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

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


void test02()
{
    //创建加法计算器
    AbstractCalculator *abc = new AddCalculator;
    abc->m_Num1 = 10;
    abc->m_Num2 = 10;
    cout << abc->m_Num1 << " + " << abc->m_Num2 << " = " << abc->getResult() << endl;
    delete abc;  //用完了记得销毁

    //创建减法计算器
    abc = new SubCalculator;
    abc->m_Num1 = 10;
    abc->m_Num2 = 10;
    cout << abc->m_Num1 << " - " << abc->m_Num2 << " = " << abc->getResult() << endl;
    delete abc;  

    //创建乘法计算器
    abc = new MulCalculator;
    abc->m_Num1 = 10;
    abc->m_Num2 = 10;
    cout << abc->m_Num1 << " * " << abc->m_Num2 << " = " << abc->getResult() << endl;
    delete abc;
}

int main() {

    //test01();

    test02();

    system("pause");

    return 0;
}

2多态之计算器类

class Base
{
public:
    //纯虚函数
    //类中只要有一个纯虚函数就称为抽象类
    //抽象类无法实例化对象
    //子类必须重写父类中的纯虚函数，否则也属于抽象类
    virtual void func() = 0;
};

class Son :public Base
{
public:
    virtual void func() 
    {
        cout << "func调用" << endl;
    };
};

void test01()
{
    Base * base = NULL;
    //base = new Base; // 错误，抽象类无法实例化对象
    base = new Son;
    base->func();
    delete base;//记得销毁
}

int main() {

    test01();

    system("pause");

    return 0;
}

3纯虚函数

//抽象制作饮品
class AbstractDrinking {
public:
    //烧水
    virtual void Boil() = 0;
    //冲泡
    virtual void Brew() = 0;
    //倒入杯中
    virtual void PourInCup() = 0;
    //加入辅料
    virtual void PutSomething() = 0;
    //规定流程
    void MakeDrink() {
        Boil();
        Brew();
        PourInCup();
        PutSomething();
    }
};

//制作咖啡
class Coffee : public AbstractDrinking {
public:
    //烧水
    virtual void Boil() {
        cout << "煮农夫山泉!" << endl;
    }
    //冲泡
    virtual void Brew() {
        cout << "冲泡咖啡!" << endl;
    }
    //倒入杯中
    virtual void PourInCup() {
        cout << "将咖啡倒入杯中!" << endl;
    }
    //加入辅料
    virtual void PutSomething() {
        cout << "加入牛奶!" << endl;
    }
};

//制作茶水
class Tea : public AbstractDrinking {
public:
    //烧水
    virtual void Boil() {
        cout << "煮自来水!" << endl;
    }
    //冲泡
    virtual void Brew() {
        cout << "冲泡茶叶!" << endl;
    }
    //倒入杯中
    virtual void PourInCup() {
        cout << "将茶水倒入杯中!" << endl;
    }
    //加入辅料
    virtual void PutSomething() {
        cout << "加入枸杞!" << endl;
    }
};

//业务函数
void DoWork(AbstractDrinking* drink) {
    drink->MakeDrink();
    delete drink;
}

void test01() {
    DoWork(new Coffee);
    cout << "--------------" << endl;
    DoWork(new Tea);
}


int main() {

    test01();

    system("pause");

    return 0;
}

纯虚函数示例-制作饮品

#include<iostream>
using namespace std;

//抽象CPU类
class CPU
{
public:
    //抽象的计算函数
    virtual void calculate() = 0;
};

//抽象显卡类
class VideoCard
{
public:
    //抽象的显示函数
    virtual void display() = 0;
};

//抽象内存条类
class Memory
{
public:
    //抽象的存储函数
    virtual void storage() = 0;
};

//电脑类
class Computer
{
public:
    Computer(CPU * cpu, VideoCard * vc, Memory * mem)
    {
        m_cpu = cpu;
        m_vc = vc;
        m_mem = mem;
    }

    //提供工作的函数
    void work()
    {
        //让零件工作起来，调用接口
        m_cpu->calculate();

        m_vc->display();

        m_mem->storage();
    }

    //提供析构函数 释放3个电脑零件
    ~Computer()
    {

        //释放CPU零件
        if (m_cpu != NULL)
        {
            delete m_cpu;
            m_cpu = NULL;
        }

        //释放显卡零件
        if (m_vc != NULL)
        {
            delete m_vc;
            m_vc = NULL;
        }

        //释放内存条零件
        if (m_mem != NULL)
        {
            delete m_mem;
            m_mem = NULL;
        }
    }

private:

    CPU * m_cpu; //CPU的零件指针
    VideoCard * m_vc; //显卡零件指针
    Memory * m_mem; //内存条零件指针
};

//具体厂商
//Intel厂商
class IntelCPU :public CPU
{
public:
    virtual void calculate()
    {
        cout << "Intel的CPU开始计算了！" << endl;
    }
};

class IntelVideoCard :public VideoCard
{
public:
    virtual void display()
    {
        cout << "Intel的显卡开始显示了！" << endl;
    }
};

class IntelMemory :public Memory
{
public:
    virtual void storage()
    {
        cout << "Intel的内存条开始存储了！" << endl;
    }
};

//Lenovo厂商
class LenovoCPU :public CPU
{
public:
    virtual void calculate()
    {
        cout << "Lenovo的CPU开始计算了！" << endl;
    }
};

class LenovoVideoCard :public VideoCard
{
public:
    virtual void display()
    {
        cout << "Lenovo的显卡开始显示了！" << endl;
    }
};

class LenovoMemory :public Memory
{
public:
    virtual void storage()
    {
        cout << "Lenovo的内存条开始存储了！" << endl;
    }
};


void test01()
{
    //第一台电脑零件
    CPU * intelCpu = new IntelCPU;
    VideoCard * intelCard = new IntelVideoCard;
    Memory * intelMem = new IntelMemory;

    cout << "第一台电脑开始工作：" << endl;
    //创建第一台电脑
    Computer * computer1 = new Computer(intelCpu, intelCard, intelMem);
    computer1->work();
    delete computer1;

    cout << "-----------------------" << endl;
    cout << "第二台电脑开始工作：" << endl;
    //第二台电脑组装
    Computer * computer2 = new Computer(new LenovoCPU, new LenovoVideoCard, new LenovoMemory);;
    computer2->work();
    delete computer2;

    cout << "-----------------------" << endl;
    cout << "第三台电脑开始工作：" << endl;
    //第三台电脑组装
    Computer * computer3 = new Computer(new LenovoCPU, new IntelVideoCard, new LenovoMemory);;
    computer3->work();
    delete computer3;

}

示例-电脑组装

posted @ 2022-07-17 16:57 风hua 阅读(42) 评论(0) 编辑收藏举报

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