C++之继承类中的this指针

最新推荐文章于 2024-08-20 19:45:24 发布

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最新推荐文章于 2024-08-20 19:45:24 发布

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分类专栏： C++

本文链接：https://blog.youkuaiyun.com/maoliran/article/details/51674227

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本文通过具体的C++代码示例，探讨了类继承中this指针的行为特性及其在抽象类与虚函数环境下的表现差异。

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#include<iostream>
#include<typeinfo>
using namespace std;

class A {
public:
    A() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "----------------------" << endl;
    }
    int a;
};
class B:public A {
public:
    B() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "&b = " << &b << endl;
        cout << "----------------------" << endl;
    }
    int b;
};
class C :public B {
public:
    C() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "&b = " << &b << endl;
        cout << "&c = " << &c << endl;
        cout << "----------------------" << endl;
    }
    int c;
};

int main() {
    A *pa = new C;
    delete pa;

    system("pause");
    return 0;
}

输出结果：

这里写图片描述

可以看到A B C 的this指针的地址都是相同的（与成员变量a的地址相同），但类型是不同的。

如果A是抽象类呢：

#include<iostream>
#include<typeinfo>
using namespace std;

class A {
public:
    A() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "----------------------" << endl;
    }
    virtual void fun() = 0;
    int a;
};
class B:public A {
public:
    B() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "&b = " << &b << endl;
        cout << "----------------------" << endl;
    }
    void fun() {}
    int b;
};
class C :public B {
public:
    C() {
        cout << this << endl;
        cout << typeid(this).name() << endl;
        cout << "&a = " << &a << endl;
        cout << "&b = " << &b << endl;
        cout << "&c = " << &c << endl;
        cout << "----------------------" << endl;
    }
    int c;
};

int main() {
    A *pa = new C;
    delete pa;

    system("pause");
    return 0;
}