有人可以解释这里发生了什么(类和构造函数/析构函数)？

Question

#include <iostream>
#include <string>

using namespace std;

class Person
{
    string name;

    public:
        Person():name("")
        {
            cout << "Person default ctor\n";
        }
        Person(const string& name_in):name(name_in)
        {
            cout << "Person string ctor: " << name << "\n";
        }
        ~Person()
        {
            cout << "Person dtor: " << name << "\n";
        }
        string get_name()
        {
            return name;
        }
};

class Professor:public Person
{
    int office;

    public:
        Professor(const string& name_in, int office_in):Person(name_in), office(office_in)
        {
            cout << "Professor string ctor: " << get_name() << endl;
        }
        ~Professor()
        {
            cout << "Professor dtro: " << get_name() << endl;
        }
};

int main()
{
    Person alice("Alice");
    Professor bob("Bob", 10);

    return 0;
}

我认为输出应该是:

Person string ctor: Alice

Person dtor: Alice

Professor string ctor: Bob

Professor dtor: Bob

因为看起来逻辑上应该遵循程序的结构.但是,实际输出是:

Person string ctor: Alice

Person string ctor: Bob

Professor string ctor: Bob

Professor dtor: Bob

Person dtor: Bob

Person dtor: Alice

有人可以解释为什么会这样吗？我怎么不理解那些让我想出错误输出的类/构造函数/析构函数？

Answer 1

首先,Professor源于Person.这意味着,每个实例Professor暗含的一个实例Person(观察你如何调用Person(name_in)中Professor的构造函数).当Professor对象被销毁时,这个隐式实例将自动被销毁.

这解释了为什么你看到:

Person string ctor: Bob
Person dtor: Bob

对于析构函数调用的顺序,变量以相反的构造顺序销毁.这解释了为什么Bob在爱丽丝之前被摧毁

Person string ctor: Alice
Professor string ctor: Bob
Professor dtor: Bob
Person dtor: Alice