面向对象程序设计-C++ Type conversion (Static) & Inheritance & Composition【第十二次上课笔记】

这节课继续讲解了　static 作为静态数据成员　/　成员函数的用法

具体详解我都已注释出来了，大家可以慢慢看

有任何问题都可以在这篇文章下留言我会及时解答　:)

//static 静态数据成员
//static 静态成员函数

#include <iostream>

using namespace std;

class Integer {
public:
    int i;        
    static int number;            //Declaration,    整个类只有一个版本，所有对象共享
    //const static int number = 49;        在C++中也可以这样定义，不过比较奇葩
    int geti () { return i; }    //名称混编: _geti@Integer_    _v (Integer * const this)
    Integer (int k = 0) : i(42) { ++number; }
    static int getNumber ();    //名称混编: geti@Integer__v ()
};

int Integer::getNumber () {        //不需要写成static int Integer::getNumber
    //++i;    无法在静态成员函数中访问非静态成员
    //        非静态成员函数只能在静态成员函数中访问
    //this->i++;
    //        静态成员函数中无 this 指针
    return number;
}

int Integer::number = 0;//Definition

int main () {

    Integer Zhao, jin, wei, shi, tian, cai;
    
    Zhao.i = 78;
    Zhao.number = 4;

    cout << Zhao.i << endl;

    cout << Zhao.getNumber () << endl;
    cout << Integer::getNumber()<< endl;

    return 0;
}

以下是　组合　的例子

组合就是一个　has a 的关系，非常好理解

/*************************************************************************
    > File Name: Code05.cpp
    > Author: Jeremy Wu
    > Created Time: Mon 18 May 2015 10:47:03 AM CST
 ************************************************************************/

#include <iostream>
#include <string>

using namespace std;

//class Building;    //类的前置声明
//Building *bd;    //前置声明无法创建对象，但可以创建指针

class Building {

};

class Student {
public:
    int xuehao;
    double chengji;
    string address;
};

class Campus {    //relation : A Campus has Building & Student
    Building bd;
    Student st;
        
};

int main (){
    


    return 0;
}

然后着重介绍了继承的相关概念

继承就是一个　is -a 的关系

/*************************************************************************
    > File Name: Code06.cpp
    > Author: Jeremy Wu
    > Created Time: Mon 18 May 2015 10:55:00 AM CST
 ************************************************************************/

//构造函数调用顺序
//先调用基类构造函数
//再创建成员
//最后调用派生类构造函数

#include <iostream>
#include <string>

using namespace std;

class Person {                        //Base class
private:    
    string name, address;
    bool sex;
protected:                            //Protected, like private, but is avaiable in derived calss
    int age;
public:
    int getAge () { return age; }
    void setAge (int i) { age = i; }
    string getName () { return name; }
    void setName (string nm) { name = nm; }
    string getAdress () { return address; }
    void setAdress (string ar) { address = ar; }
    bool getSex () { return sex; }
    void setSex (bool sx) { sex = sx; }

    Person (string nm, string ar, int a, bool s) 
        : name (nm), address (ar), age (a), sex (s) {
            cout << "Person (string nm, string ar, int a, bool s) is called" << endl;
        }
    ~Person () { cout << "~Person () is called" << endl; }
};

class Test {
public:
    Test () { cout << "Test () is  called" << endl; }
    ~Test () { cout << "~Test () is called" << endl; }
};

class Student : private Person {        //Derived class
                                    //relation : A student is a person
                                    //if private derived, all the public funcions will be private as well as member varible
    //Person ps;
    Test t;
    unsigned int id;
public:
    int getId () { return id; }
    int setId (unsigned int id) { this->id = id; }
    
    void addAge () { ++age;    }
    //void addAge () { setAage (getAge () + 1 ); } //low efficiency

    Student (string nm, string ar, int a, bool s, unsigned int xh) 
        : Person (nm, ar, a, s), id (xh) {
            cout << "Student (string nm, string ar, int a, bool s, unsigned int xh) is called" << endl; 
        }
    ~Student () { cout << "~Student () is called" << endl; }

};
 
class UniversityStudent : public Student {
    //void print () { getName (); } 基类需要保护继承
};

void print (Person *p) {
    cout << p->getAge () << endl
        << p->getName () << endl
        << p->getAdress () << endl
        << p->getSex () << endl;
        //<< p->setId () << endl;    //Object slice 对象剪切
}

int main () {

    Person ps ("Zhao jinwei", "U.S.A", 20, true);
    Student st ("Ph.D Zhao", "CHINA", 20, false, 1322);

    //cout << st.getAge () << endl;
    st.addAge ();
    //ps.addAge ();
    cout << st.getName () << " " << st.getAge () << endl; //派生类对象继承了基类中成员
    print (&st); 

    return 0;
}