子类虚函数中关键字override有什么用？[重复]

Question

未解决原始关闭原因

关键字虚拟允许派生类在需要多态的情况下覆盖，这可以在有或没有关键字覆盖的情况下关闭。添加覆盖如何影响程序？

示例代码：

#include <iostream>
using namespace std;

class Base {
public:
    void Print() {who();}
    virtual void who() { cout << "I am Base\n"; }
};
class Derived_A : public Base {
public:
    void who() { cout << "I am Derived_A\n"; }
};
class Derived_B : public Base {
public:
    virtual void who() override { cout << "I am Derived_B\n"; }
};

int main()
{
    Base b;
    b.Print(); //-> return "I am Base"

    Base* ptr = new Derived_A();
    ptr->Print(); // was expecting "I am Base" instead returns "I am Derived_A"

    Base* ptr1 = new Derived_B();
    ptr1->Print(); // expecting "I am Derived_B" and surely returns "I am Derived_B"

    return 0;
}

Answer 1

向成员函数添加< code>override不会以任何方式改变程序的工作方式。你只需告诉编译器你想重写一个基类函数，如果你犯了一个错误，你会得到一个编译错误，以为你在重写一个函数，而实际上你没有。

例子：

class Base {
public:
    virtual void foo(int) {}
};

class Derived : public Base {
public:
    void foo(double) override {} // compilation error
};