在不使用public或private的情况下继承其他类 [英] Inheriting other class without using public or private

问题描述

尊敬的老年人，
您能否在不指定public或private的情况下给出一些关于我到底如何能够继承其他类的功能的提示.如果我能够，那么什么时候才应该使用公共或私人
以下是示例代码段供您参考.

Dear Seniors,
Can you please give some hints on how exactly i am able to inherit the functions of other class with out specifying either public or private. If i am able to then when only should I use public or private
Below is the sample code snippet for your reference.

#include <iostream>
#include <string>

class A
{
    private:
        std::string name;
    public:
        void getdata( )
        {
            std::cout << "Name: ";
            std::cin  >> name;
        }
        void showdata( )
        {
            std::cout << "Your name: " << name << std::endl;
        }
};

class B
{
    private:
        std::string surname;
        A a;
    public:
        void getdata( )
        {
            a.getdata( );
            std::cout << "Surname: ";
            std::cin  >> surname;
        }
        void showdata( )
        {
            a.showdata( );
            std::cout << "Your surname: " << surname << std::endl;
        }
};

int main( )
{
    B e;
    e.getdata( );
    e.showdata( );
    return 0;
}

问候，
Kiran

Regards,
Kiran

推荐答案

这里根本没有继承.
您只是在创建class A的对象作为class B的成员变量.
这与在类内部或main函数中的class B对象中创建std::string对象的方式相同.
因此，例如，您将无法执行任何多态性.
A* ptr = new B;将引发错误，因为这需要继承.

There is no inheritance here at all.
You''re simply creating an object of class A as a member variable of class B.
This is the same as how you created a std::string object inside the class or an object of class B in the main function.
So, for example, you will not be able to perform any polymorphism.
A* ptr = new B; will throw an error because this needs inheritance.

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