嘀嘀咕

Posted 2021-01-16 engineerzhang

目录

• 1.继承
  • 父类指针可以指向子类对象
  • 父类、子类出现重名变量
  • 继承中构造和析构
• 2.多继承、虚继承

1.继承

class Student
{
public:
    Student()
    {

    }
    Student(int id, string name)
    {
        this->id = id;
        this->name = name;
    }

    void printS() {
        cout << "id = " << this->id << ", name = " << this->name << endl;
    }
    int id;
    string name;
};




//通过继承创建一个新的学生类
class Student2 :public Student
{
public:
    Student2(int id, string name, int score) :Student(id, name)        //调用父类构造函数
    {

        this->score = score;
    }

    void printS() {
        Student::printS();
        cout << "score = " << this->score << endl;
    }
private:
    int score;
};

private成员在子类中依然存在，但是却无法访问到。不论何种方式继承基类，派生类都不能直接使用基类的私有成员  。

父类指针可以指向子类对象

void myPrint(parent *p)
{
}

myPrint(&p);
myPrint(&c);

父类、子类出现重名变量

class Parent
{
public:
    Parent(int a) {
        this->a = a;
    }

    int a;
};

class Child :public Parent
{
public:
    Child(int p_a, int c_a) :Parent(p_a)
    {
        this->a = c_a;
    }

    void print()
    {
        cout << Parent::a << endl;
        cout << this->a << endl;//child‘s a
    }
    int a;
};

继承中构造和析构

先构造父类，再构造成员变量、最后构造自己
先析构自己，在析构成员变量、最后析构父类

class Object
{
public:
     Object(const char* s)
     {
           cout<<"Object()"<<"  "<<s<<endl;
     }
     ~Object()
     {
           cout<<"~Object()"<<endl;
     }
};

class Parent : public Object
{
public:
     Parent(const char* s) : Object(s)
     {
           cout<<"Parent()"<<"  "<<s<<endl;
     }
     ~Parent()
     {
           cout<<"~Parent()"<<endl;
     }
};

class Child : public Parent
{
public:
     Child() : o2("o2"), o1("o1"), Parent("Parameter  from  Child!")
     {
           cout<<"Child()"<<endl;
     }
     ~Child()
     {
           cout<<"~Child()"<<endl;
     }
private:
     Object o1;
     Object o2;
};

void run()
{
     Child child;
}

int main(int argc, char *argv[])
{
     run();
     return 0;
}

2.多继承、虚继承

//家具类
class Furniture
{
public:
    int m; //材质
};

//将父亲类继承爷爷类  改成虚继承， 防止儿子在多继承的时候，出现爷爷中的变量会拷贝多份。
class Bed:virtual public Furniture
{
public:
    void sleep() {
        cout << "在床上睡觉" << endl;
    }
};


class Sofa:virtual public Furniture
{
public:
    void sit() {
        cout << "在沙发上休息" << endl;
    }
};

//沙发床
class SofaBed :public Bed, public Sofa
{
public:
    void SleepAndSit() {
        sleep();
        sit();
    }
};