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- 子类对象会继承基类的属性的行为，任何时候子类对象都可以被当做基类类型的对象，通过子类对象可以直接访问基类中的成员，如同是基类对象在访问它们一样
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向上造型和向下造型
- 向上造型(upcast)：将子类类型的指针或引用转换为基类类型的指针或引用；这种操作性缩小的类型转换，在编译器看来是安全的，可以隐式转换
- 向下造型(downcast)：将基类类型的指针或引用转换为子类类型的指针或引用；这种操作性放大的类型转换，在编译器看来是危险的，不能隐式转化，但是可以显式转换
#include<iostream>usingnamespacestd;classHuman{private:intm_private;protected:string m_name;intm_age;constint&get(void){returnm_private;}public:Human(conststring&name,intage){m_name=name;m_age=age;m_private=1234;}voideat(conststring&food){cout<<"我在吃: "<<food<<endl;}voidsleep(inthour){cout<<"我睡了"<<hour<<"小时"<<endl;}};classStudent:publicHuman{private:intm_no;//学号public:Student(conststring&name,intage,intno):Human(name,age){m_no=no;}voidwho(void){cout<<"我叫: "<<m_name<<", 今年"<<m_age<<"岁，学号是: "<<m_no<<endl;//cout << m_private << endl; //errorcout<<get()<<endl;}voidlearn(conststring&course){cout<<"我在学"<<course<<endl;}};classTeacher:publicHuman{private:intm_salary;public:Teacher(conststring&name,intage,intsalary):Human(name,age),m_salary(salary){}voidteach(conststring&course){cout<<"我正在讲 "<<course<<endl;}voidwho(void){cout<<"我叫 "<<m_name<<",今年"<<m_age<<"岁, 工资是"<<m_salary<<endl;}};intmain(void){Students("张飞",28,100011);cout<<"sizeof(s) = "<<sizeof(s)<<endl;s.who();s.eat("宫保鸡丁");s.sleep(8);s.learn("C++编程");Teachert("诸葛亮",34,200000);t.who();t.teach("嵌入式");t.sleep(7);t.eat("汉堡");// Student * -----> Human *:向上造型Human*ph=&s;ph->eat("香蕉");ph->sleep(10);//ph->who(); //error// Human * --------> Student *: 向下造型（合理）Student*ps=static_cast<Student*>(ph);ps->who();Humanh("赵云",22);//Human * -------> Student *: 向下造型 (不合理)Student*ps2=static_cast<Student*>(&h);ps2->who();return0;}
成员函数的重定义（名字隐藏）
- 重定义: 简单的说就是子类中定义了和父类的同名函数，对父类的成员函数造成了隐藏
#include<iostream>usingnamespacestd;classBase{private:intx;public:voidset(inti){x=i;}voidprint(){cout<<"Base class "<<"x= "<<x<<endl;}};classDerived:publicBase{private:intm,n;public:voidset(intp,intk){m=p;n=k;}voidprint(){Base::print();cout<<"Derived class "<<"m = "<<m<<", n="<<n<<endl;}};intmain(void){Derived d;d.set(10,20);//d.set(100); // error 名字隐藏d.Base::set(100);d.print();return0;}
