文章标题

#include <iostream>#include <string>using namespace std;class Base{public:    Base()    {        cout << "Base::基类" << endl;    }    ~Base()    {        cout << "调用基类的析构函数" << endl;    };    // 成员初始化列表语法    Base(string x,string y):x(x),y(y)    {        cout << "Base::传递参数的基类构造函数" << endl;    };private:    string x;    string y;};class Derive:public Base    // 派生   公有派生// 使用公有派生，基类的公有成员将成为派生类的公有成员。// 基类的私有部分也将成为派生类的一部分，但只能通过基类的公有和保护方法访问。// 派生类不能直接访问基类的私有成员，而必须通过基类方法进行访问。{public:    Derive()    {        cout << "Derive::派生" << endl;    }    ~Derive()    {        cout << "调用派生类的析构函数" << endl;    };    // 成员初始化列表语法    Derive(string z,string str2,string str3):Base(str2,str3),z(z)    {        //this.z = z;        cout << "Derive::传递参数的派生类的构造函数" << endl;    }    Derive(string z,const Base & base):Base(base),z(z)    {        cout << "Derive::传递参数的派生类的构造函数" << endl;    }private:    string z;};int main(){    // 基类对象应该在程序进入派生类构造函数之前被创建。    Derive *derive;    derive = new Derive("10","10","10");    delete derive;    cout << endl;    cout << "********************" << endl;    Base *base = new Base("20","20");    derive = new Derive("BG_80",*base);    //delete base;    // 派生类过期时，程序首先调用派生类的析构函数，然后调用基类的析构函数。    delete derive;              // 这里要不要delete base? 应该不要    system("pause");    return 0;}

如果子类中没有默认无参构造函数，那么像下面这样调用会报错

#include <iostream>using namespace std;class A{public:    int a;    int b;// A()// {//  cout<<"A Constructed 1\n";// }A(int a,int b){    this->a=a;    this->b=b;    cout<<"A Constructed 2\n";}};class B:public A{public:    int c;    int d;B(){    cout<<"B Constructed 1\n";}B(int c,int d):A(100,200){    this->c=c;    this->d=d;    cout<<"B Constructed 2\n";}};int main(){    // B b(1,1);    // cout << "b.a = " << b.A::a <<" " << "b.b = " << b.A::b << endl;    // cout << "b.a = " << b.a <<" " << "b.b = " << b.b << endl;    // cout << "b.c = " << b.c <<" " << "b.d = " << b.d << endl;    B b;    return 0;}