note.c++.inherit_virtual_and_member.md

id	title	desc	updated	created
x3ue6km5bcnxl3lgzz45h96	Inherit_virtual_and_member		1696922682461	1696921298138

use case of virtual

• directly call virtual outside to the class
• call virtual method inside to class member function, then derived class just modify the virtual and still call the member of base class outside

#include <stdio.h>
#include <iostream>
class Base {
public:
    virtual void foo() {
        std::cout << "Base::foo()" << std::endl;
    }
    void bar() {
        std::cout << "Base::bar() calling foo()" << std::endl;
        foo(); // 这里调用的是虚函数 foo()
    }
};
class Derived : public Base {
public:
    void foo() override {
        std::cout << "Derived::foo()" << std::endl;
    }
};
int main() {
    Derived d;
    Base& b = d; // 向上转型，将 Derived 对象引用绑定到 Base 类型的引用上

    b.bar(); // 调用 Base 类的 bar() 函数
    printf("enter second!\n");
    
    Base* bb = new Derived{};
    bb->bar();
    return 0;
}

• call virtual method inside to class virtual member function

#include <stdio.h>
#include <iostream>
class Base {
public:
    virtual void foo() {
        std::cout << "Base::foo()" << std::endl;
    }

    virtual void bar() {
        std::cout << "Base::bar() calling foo()" << std::endl;
        foo(); // 这里调用的是虚函数 foo()
    }
};

class Derived : public Base {
public:
    void foo() override {
        std::cout << "Derived::foo()" << std::endl;
    }
    void bar() {
        std::cout << "Derived::bar() calling foo()" << std::endl;
        foo(); // 这里调用的是虚函数 foo()
        Base::foo();
    }
};

int main() {
    Derived d;
    Base& b = d; // 向上转型，将 Derived 对象引用绑定到 Base 类型的引用上

    b.bar(); // 调用 Base 类的 bar() 函数
    printf("enter second!\n");
    
    Base* bb = new Derived{};
    bb->bar();
    return 0;
}

example

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