C++_day7_继承

#include <iostream>

using namespace std;

class Human{

public:

    Human(string const& name, int age):m_name(name), m_age(age)

    {

        cout << "Human构造：" << this << endl;

    }

    ~Human(void)

    {

        cout << "Human析构："<< this << endl;

    }

    void eat(string const& food)

    {

        cout << "I am eating " << food << '.' << endl;

    }

    void sleep(string const& loc)

    {

        cout << "I am sleepping at " << loc << endl;

    }

    void who(void)

    {

        cout << "My name is " << m_name << ", I'm " << m_age << " years old." << endl;

    }

    string m_name;

    int m_age;

};

class Student: public Human{

public:

    Student(string const& name, int age, int no):Human(name, age), m_no(no)

    {

        cout << "Student构造：" << this << ' ' << &m_no << endl;

    }

    ~Student(void)

    {

        cout << "Student析构："<< this << endl;

    }

    void learn(string const& course)

    {

        cout << "I am a student, My no is " << m_no << ", I am learning " << course << '.' << endl;

    }

    int m_no;

private:

    int m_a;

protected:

    int m_c; //子类可以访问

};

class Teacher: public Human{

public:

    Teacher(string const& name, int age, float salary):Human(name, age), m_salary(salary)

    {

        cout << "Teacher构造：" << this <<' ' << &m_salary << endl;

    }

    ~Teacher(void)

    {

        cout << "Teacher析构："<< this << endl;

    }

    void teach (string const& course)

    {

        cout << "I am a teacher, My salary is " << m_salary << ", I'm teaching " << course << '.' << endl;

    }

    float m_salary;

};

int main(void)

{

    Student s1("WJ Zhang", , );

    cout << s1.m_name << endl;

    cout << s1.m_age << endl;

    cout << s1.m_no << endl;

    s1.who();

    s1.eat("noodle");

    s1.sleep("floor");

    s1.learn("C++");

    Teacher t1("SF Zhang", , );

    cout << t1.m_name << endl;

    cout << t1.m_age << endl;

    cout << t1.m_salary << endl;

    t1.who();

    t1.eat("chicken");

    t1.sleep("sofa");

    t1.teach("C++");

    cout << sizeof(Human) << endl;

    cout << sizeof(Student) << endl;

    cout << sizeof(Teacher) << endl;

    cout << sizeof(string) << endl;

    Human* ph = &s1;    //is a ...

    cout << ph->m_name << endl;

    cout << ph->m_age << endl;

    //cout << ph->m_no << endl;    //error: ‘class Human’ has no member named ‘m_no’

    ph->who();

    Student* ps = static_cast<Student*>(ph);

    cout <<ps->m_no << endl;

    /*导致风险

    Human h1("ZR Zhou", 18);

    ps = static_cast<Student*> (&h1);

    cout << ps->m_no << endl;

    ps->learn("123");

    */

    /*谨慎慎用对象截切

    Human h1 = s1;

    cout << h1.m_name << endl;

    cout << h1.m_age << endl;

    */

    return ;

}