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网站的营销策略,如何做一个免费网页,外贸网站支付系统,广告优化师前景一、继承方式1. 单继承一个派生类只有一个直接基类的时候称这个继承为单继承 Person ↓ Teacher ↓ Student #xff08;单链#xff09;代码语言#xff1a;javascriptAI代码解释// 基类#xff1a;人 class Person { public:string name;int age;void ShowPerson(){cout …一、继承方式1. 单继承一个派生类只有一个直接基类的时候称这个继承为单继承 Person ↓ Teacher ↓ Student 单链代码语言javascriptAI代码解释// 基类人 class Person { public: string name; int age; void ShowPerson() { cout 姓名: name 年龄: age endl; } }; // 派生类老师继承人 class Teacher : public Person { public: string subject; void ShowTeacher() { cout 姓名: name 年龄: age 教授科目: subject endl; } }; // 派生类学生继承老师 class Student : public Teacher { public: string school; void ShowStudent() { cout 姓名: name 年龄: age 教授科目: subject 学校: school endl; } }; int main() { Student s; s.name 呆头; // 来自 Person s.age 20; // 来自 Person s.subject C; // 来自 Teacher s.school 野鸡大学; // 来自 Student s.ShowStudent(); return 0; }运行结果在这里插入图片描述多链在这里插入图片描述代码语言javascriptAI代码解释// 基类人 class Person { public: string name; int age; void ShowPerson() { cout 姓名: name 年龄: age endl; } }; // 派生类老师 class Teacher : public Person { public: string subject; void Teach() { cout name 正在教授 subject 课程。 endl; } }; // 派生类学生 class Student : public Person { public: string school; void Study() { cout name 在 school 学习。 endl; } }; int main() { Teacher t; t.name 张老师; t.age 35; t.subject C; t.ShowPerson(); t.Teach(); cout ------------------ endl; Student s; s.name 李华; s.age 20; s.school 宁夏大学; s.ShowPerson(); s.Study(); return 0; }2. 多继承一个派生类有两个或者以上的直接基类时称这个继承关系为多继承多继承对象在内存中的模型是先继承的基类在前面后继承的基类在后面派生类成员放在最后面。多继承的使用方法是在子类的位置对多个父类使用逗号进行间隔其余方式public形式不变进行继承代码语言javascriptAI代码解释Person Teacher Athlete \ | / \ | / ---- Student代码语言javascriptAI代码解释// 基类人 class Person { public: string name; int age; }; // 老师类 class Teacher { public: string subject; void Teach() { cout 正在教授 subject 课程。 endl; } }; // 运动员类 class Athlete { public: string sport; void Train() { cout 正在训练 sport 项目。 endl; } }; // 学生类多继承 class Student : public Person, public Teacher, public Athlete { public: string school; void Show() { cout 姓名: name 年龄: age 学校: school 教授科目: subject 运动项目: sport endl; } }; int main() { Student s; s.name 李华; s.age 20; s.school 宁夏大学; s.subject C; s.sport 800米; s.Show(); s.Teach(); s.Train(); return 0; }运行结果在这里插入图片描述3. 菱形继承菱形继承是多继承的⼀种特殊情况。菱形继承的问题有数据冗余和⼆义性的问题。⽀持多继承就⼀定会有菱形继承像Java就直接不⽀持多继承规避掉了这⾥的问题所以实践中我们也是不建议设计出菱形继承这样的模型的。在这里插入图片描述代码语言javascriptAI代码解释#include iostream #include string using namespace std; // 基类人 class Person { public: string name; int age; }; // 老师继承人 class Teacher : public Person { public: string subject; void Teach() { cout name 正在教授 subject endl; } }; // 运动员继承人 class Athlete : public Person { public: string sport; void Train() { cout name 正在训练项目 sport endl; } }; // 学生同时继承老师与运动员 class Student : public Teacher, public Athlete { public: string school; void Show() { // ⚠️ 错误编译器不知道 name 是哪个基类的 // cout 姓名: name endl; // ❌ 二义性 cout Teacher::name Teacher::name endl; cout Athlete::name Athlete::name endl; cout 学校: school endl; } }; int main() { Student s; s.Teacher::name 张老师; s.Athlete::name 李同学; // 各自一份 name s.subject C; s.sport 800米; s.school 宁夏大学; s.Show(); // 访问需要显式指定路径 s.Teacher::Teach(); s.Athlete::Train(); return 0; }Student ├── Teacher::Person │ ├── name │ └── age ├── Athlete::Person │ ├── name │ └── age └── school在这里插入图片描述在这里插入图片描述在这里插入图片描述3.1 菱形虚拟继承如何解决菱形继承带来的弊端——》使用虚拟继承 以上述对象模型为例在 Teacher 和 Athlete 继承 Person 时采用虚拟继承即可避免 Student 同时拥有两份 Person 子对象。虚拟继承是一种专门用于解决菱形继承问题的机制在其它普通继承场景下不建议使用。在 C 中虚拟继承的使用方式是当多个派生类继承自同一个公共基类并且这些派生类又被同一个子类多继承时应当在这些“中间层”父类继承公共基类的地方使用 virtual 关键字进行修饰。(上述示例就应该在老师和运动处使用virtual进行修饰)代码语言javascriptAI代码解释class Person { public: string name; int age; }; // 老师虚继承人 class Teacher : virtual public Person { public: string subject; }; // 运动员虚继承人 class Athlete : virtual public Person { public: string sport; }; // 学生多继承 class Student : public Teacher, public Athlete { public: string school; void Show() { cout 姓名: name endl; // ✅ 不再二义性 cout 学校: school endl; } };3.2 菱形虚拟继承的原理回顾我们上述示例是这样的继承关系代码语言javascriptAI代码解释Person / \ Teacher Athlete \ / Student如果Student同时继承Teacher和Athlete他就会有两份Person成员一次从Teacher一次从Athlete这样会造成数据冗余。调用Student的Person的成员函数或者访问成员变量的时候编译器就不知道选择Teacher中的还是Athlete中的那一份就造成了二义性。3.2.1 内存布局虚拟继承会让共享的基类在内存中只有一份并且派生类通过虚基表vbt/vptr类似来找到这份共享的基类。代码语言javascriptAI代码解释Student 对象布局虚继承 [ Student 部分 ][ Teacher 部分 ][ Athlete 部分 ][ Person(共享) ]注意Person只存在一份。每个通过虚继承的中间类Teacher、Athlete内部不直接包含Person成员而是包含一个指向共享Person的指针实际上是偏移量。当Student被实例化时最终会在对象末尾放置一份Person数据。所有通过虚继承的类访问Person时通过偏移量找到唯一的Person。示意图代码语言javascriptAI代码解释Student 内存 [ Student fields ] [ Teacher fields | pointer_to_shared_Person ] [ Athlete fields | pointer_to_shared_Person ] [ Shared Person fields ]3.2.2 虚表vtable/vptr调整虚继承通常涉及两个表普通虚表用于多态函数调用。虚基表VBT用于找到虚继承基类的偏移量。访问虚基类成员时编译器生成代码不是this offset_of_Person_in_Teacher。而是this vbt_offset→ 找到唯一Person。举例代码语言javascriptAI代码解释Student s; s.Teacher::Person::name Alice; // 编译器查找 Teacher 的虚基表 - 定位到 Student 中唯一的 Person底层逻辑this是Student的起始地址 → 查找虚基表中的Person偏移量 → 访问共享Person。3.2.3 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