C++:是“虚拟的"继承给所有后代 [英] C++: Is "Virtual" inherited to all descendants

问题描述

假设以下简单情况(注意virtual的位置)

Assume the following simple case (notice the location of virtual)

class A {
    virtual void func();
};

class B : public A {
    void func();
};

class C : public B {
    void func();
};

下面的调用会调用 B::func() 还是 C::func()?

Would the following call call B::func() or C::func()?

B* ptr_b = new C();
ptr_b->func();

推荐答案

使用指针和引用的示例.

Examples using pointers as well as reference.

• 使用指针

• Using pointer

B *pB = new C();
pB->func(); //calls C::func()

A *pA = new C();
pA->func(); //calls C::func()

使用参考.注意最后一个电话:最重要的电话.

Using reference. Note the last call: the most important call.

C c;
B & b = c;
b.func(); //calls C::func() 

//IMPORTANT - using reference!
A & a = b;
a.func(); //calls C::func(), not B::func()

在线演示:http://ideone.com/fdpU7

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