从构造函数调用虚函数 [英] Virtual function invocation from constructor

问题描述

也许我错了，但这似乎是一个非常基本的问题。突然我的继承链停止工作。写一个小的基本测试应用程序证明是我是错误的（所以我不能怪编译器）。

Maybe I am wrong, but this seems to be a very basic question. Suddenly my inheritance chain stopped working. Writing a small basic test application proved that it was me that was wrong (so I can't blame the compiler).

我有一个基类，在虚函数中。

I have a base class, with the default behavior in a virtual function. A child class derives from that and changes the behavior.

#include <iostream>

class Base
{
public:
    Base() { print(); }
    ~Base() {}

protected:
    virtual void print() { std::cout << "base\n"; }
};

class Child : public Base
{
public:
    Child() {}
    ~Child() {}

protected:
    virtual void print() { std::cout << "child\n"; }
};

int main()
{
    Base b;
    Child c;
}

打印：

base
base

是创建，为什么是Base :: print（）调用？我认为通过使用virtual关键字，该函数可以替换为派生类。

When a Child instance is created, why is Base::print() called? I thought that by using the virtual keyword, the function can be replaced for the derived class.

我在什么时候感到困惑？

At what point did I get myself confused?

推荐答案

另请参见这个StackOverflow问题。

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