C++——this指针和继承

在普通的成员函数中，不管有没有定义形参
系统都会自动的加上一个隐藏的形参
该形参的类型为该类的指针类型-->（Score *）
该指针的作用：用来存放当前调用该成员函数对象的地址
一般将该指针称为this指针
Score::inScore(&s);
this->m_iNum;

特殊的成员函数

static
static 没有 this 指针
static 既可以通过类对象调用，也可以通过类名调用
static 函数中不能访问和操作普通的成员变量，
只能访问和操作静态的成员变量
一般将不需要访问和操作普通的成员变量的函数
但又和该类相关的函数申明定义为 static 成员函数
如果 static 成员变量在类外定义，则不需要加关键字 static

const
void show() const
有隐藏的 this 指针
由于成员函数声明为 const 成员函数，
该 this 指针会转变成为：const show *this
不能修改普通成员变量的值 -->const Show *this
但是可以修改静态成员变量 static 的值
一般将只访问不涉及修改成员变量的函数
申明为const成员函数，以防意外修改了成员变量
const成员函数只能被类对象调用

继承

多继承

虚继承（选择继承，多级继承可去重）
class Teacher: virtual public person
派生类会自动在类中添加一个指针
通过该指针来访问基类数据
由最派生类来真正继承被虚继承的类
被虚继承的类中的成员的初始化由最派生类来负责

#include 
using namespace std;

class Score
{
public:
    //在普通的成员函数中，不管有没有定义形参
    //系统都会自动的加上一个隐藏的形参
    //该形参的类型为该类的指针类型--> (Score *)
    //该指针的作用：用来存放当前调用该成员函数对象的地址
    //一般将该指针称之为this指针
#if 0
    void inScore(Score *this)
    {
        cin >> this->m_iNum >> this->m_fMath 
            >> this->m_fEnglish >> this->m_fProgramming;
        this->m_fAvgScore = (this->m_fMath+this->m_fEnglish
                      +this->m_fProgramming)/3;
    }
#endif
    void inScore()
    {
        cin >> m_iNum >> m_fMath 
            >> m_fEnglish >> m_fProgramming;
        m_fAvgScore = (m_fMath+m_fEnglish
                      +m_fProgramming)/3;
    }
    void showScore()
    {
        cout << "id:" << m_iNum 
             << " score:" << m_fMath
             << ' ' << m_fEnglish 
             << ' ' << m_fProgramming 
             << " avgScore:" << m_fAvgScore << endl;
    }
    
    //1,static函数没有this指针
    //2,static函数既可以通过类对象调用，
    //  也可以通过类名调用
    //3,static函数中不能访问和操作普通的成员变量
    //  只能访问和操作静态的成员变量
    //4,一般将不需要访问和操作普通的成员变量的函数
    //  但又和该类相关的函数申明定义为static成员函数
    //5,如果static成员变量在类外定义,则返回值类型前
    //  不需要加static关键字
    static void showHappy()
    {
        //cout << m_iNum << endl;
        cout << m_iTestData << endl;
        int iData = 90;
        cout << "iData=" << iData << endl;
        cout << "I am no.1, hahahahaha..." << endl;
    }
    static Score &getInstance();
private:
    int m_iNum;
    float m_fMath;
    float m_fEnglish;
    float m_fProgramming;
    float m_fAvgScore;
    static int m_iTestData; 
};

Score& Score::getInstance()
{
    static Score s;
    return s;
}

int Score::m_iTestData = 19999;

int main(void)
{
    Score s;
    Score s2;

    s.showHappy();
    Score::showHappy();

    Score &ref = Score::getInstance();

    return 0;
}

#include 
#include 
using namespace std;

class Person
{
public:
    Person(){cout << "Person()...\n";}
    Person(string id, string name
           , int age, char sex, string addr)
    {
        m_strId = id;
        m_strName = name;
        m_iAge = age;
        m_cSex = sex;
        m_strAddress = addr;
        cout << "Person(paragms..)...\n";
    }
    void info() const
    {
        cout << m_strId << ' ' << m_strName
             << ' ' << m_iAge << ' ' << m_cSex
             << ' ' << m_strAddress << endl;
    }
private:
    string m_strId;
    string m_strName;
    int m_iAge;
    char m_cSex;
    string m_strAddress;
};

//1,继承方式：public,protected,private
//  继承方式其实是对继承过来的成员进行封装
//2,若没有指定继承方式，则默认为private继承
//  class Teacher: Person-->class Teacher: private Person
//3,只有一个继承,称之为单继承
//4,将被继承的类称之为基类
//5,新产成的类称之为派生类
//6,派生类需要对继承过来的数据和本身新增成员进行初始化
//7,对继承过来的成员初始化方式：
//  在派生类构造函数的初始化列表中，
//  显式或者隐式的调用基类的构造函数来对数据进行初始化
//  隐式的调用基类的构造函数:默认调用基类的无参构造函数
class Teacher: public Person
{
public:
#if 0
    //以下两种情况：默认调用基类的无参构造函数
    //              对继承过来的数据进行初始化
    //即没有在派生类的初始化列表中写上基类的构造函数
    //则默认调用基类的无参构造函数对继承过来的数据进行初始化
    Teacher(){cout << "Teacher()...\n";}
    Teacher(string courseName, float salary)
    {
        cout << "Teacher(paramgms..)...\n";
    }
#endif
    //Teacher(): Person()
    Teacher(): Person("000", "newperson", 0, 'm', "china")
    {
        cout << "Teacher()...\n";
    }
    //Teacher(string courseName, float salary):Person()
    Teacher(string id, string name
            , int age, char sex, string addr
            , string courseName, float salary)
        : Person(id, name, age, sex, addr)
    {
        m_strCourseName = courseName;
        m_fSalary = salary;
        cout << "Teacher(paramgms..)...\n";
    }

    void info()
    {
        Person::info();
        cout << m_strCourseName << ' ' << m_fSalary << endl;
    }

private:
    string m_strCourseName;
    float m_fSalary;
};

int main(void)
{
#if 0
    Person p("1001", "zhangsan", 18, 'f', "shanghai");
    p.info();

#endif
    //Teacher tec;
    //Teacher tec2("chinese", 9000);
    Teacher tec("1001", "xiaohua", 28, 'f', "nanhai"
                , "english", 9000);
    tec.info();

    return 0;
}

#include 
#include 
using namespace std;

class Person
{
public:
    Person(){cout << "Person()...\n";}
    Person(string id, string name
           , int age, char sex, string addr)
    {
        m_strId = id;
        m_strName = name;
        m_iAge = age;
        m_cSex = sex;
        m_strAddress = addr;
        m_strFace = "cool";
        cout << "Person(paragms..)...\n";
    }
    void info() const
    {
        cout << m_strId << ' ' << m_strName
             << ' ' << m_iAge << ' ' << m_cSex
             << ' ' << m_strAddress << endl;
    }
    string m_strFace;
private:
    string m_strId;
    string m_strName;
    int m_iAge;
    char m_cSex;
    string m_strAddress;
};

//1,继承方式：public,protected,private
//  继承方式其实是对继承过来的成员进行封装
//2,若没有指定继承方式，则默认为private继承
//  class Teacher: Person-->class Teacher: private Person
//3,只有一个继承,称之为单继承
//4,将被继承的类称之为基类
//5,新产成的类称之为派生类
//6,派生类需要对继承过来的数据和本身新增成员进行初始化
//7,对继承过来的成员初始化方式：
//  在派生类构造函数的初始化列表中，
//  显式或者隐式的调用基类的构造函数来对数据进行初始化
//  隐式的调用基类的构造函数:默认调用基类的无参构造函数
//class Teacher: public Person
//class Teacher: protected Person
class Teacher: private Person
{
public:
#if 0
    //以下两种情况：默认调用基类的无参构造函数
    //              对继承过来的数据进行初始化
    //即没有在派生类的初始化列表中写上基类的构造函数
    //则默认调用基类的无参构造函数对继承过来的数据进行初始化
    Teacher(){cout << "Teacher()...\n";}
    Teacher(string courseName, float salary)
    {
        cout << "Teacher(paramgms..)...\n";
    }
#endif
    //Teacher(): Person()
    Teacher(): Person("000", "newperson", 0, 'm', "china")
    {
        cout << "Teacher()...\n";
    }
    //Teacher(string courseName, float salary):Person()
    Teacher(string id, string name
            , int age, char sex, string addr
            , string courseName, float salary)
        : Person(id, name, age, sex, addr)
    {
        m_strCourseName = courseName;
        m_fSalary = salary;
        cout << "Teacher(paramgms..)...\n";
    }

    void info()
    {
        Person::info();
        cout << m_strCourseName << ' ' << m_fSalary << endl;
        cout << m_strFace << endl;
        //cout << m_strName << endl;
    }

private:
    string m_strCourseName;
    float m_fSalary;
};
//class Test:public Person;
int main(void)
{
    Teacher tec("1001", "xiaohua", 28, 'f', "nanhai"
                , "english", 9000);
    tec.info();

//  cout << tec.m_strFace << endl;

    return 0;
}

//多继承
#include 
#include 
using namespace std;

class Person
{
public:
    Person(){cout << "Person()...\n";}
    Person(string id, string name
           , int age, char sex, string addr)
    {
        m_strId = id;
        m_strName = name;
        m_iAge = age;
        m_cSex = sex;
        m_strAddress = addr;
        cout << "Person(paragms..)...\n";
    }
    void info() const
    {
        cout << m_strId << ' ' << m_strName
             << ' ' << m_iAge << ' ' << m_cSex
             << ' ' << m_strAddress << endl;
    }
private:
    string m_strId;
    string m_strName;
    int m_iAge;
    char m_cSex;
    string m_strAddress;
};
//虚继承,派生类会自动在类中添加一个指针
//通过该指针来访问基类数据
class Teacher: virtual public Person
{
public:
    Teacher()
    {
        cout << "Teacher()...\n";
    }
    //Teacher(string courseName, float salary):Person()
    Teacher(string id, string name
            , int age, char sex, string addr
            , string courseName, float salary)
        : Person(id, name, age, sex, addr)
    {
        m_strCourseName = courseName;
        m_fSalary = salary;
        cout << "Teacher(paramgms..)...\n";
    }

    void info() const
    {
        Person::info();
        cout << m_strCourseName << ' ' << m_fSalary << endl;
    }

private:
    string m_strCourseName;
    float m_fSalary;
};

class Student: virtual public Person
{
public:
    Student()
    {
    }
    Student(string id, string name
            , int age, char sex, string addr
            , float math, float chinese
            , float english, string grade)
        : Person(id, name, age, sex, addr)
    {
        m_fMath = math;
        m_fChinese = chinese;
        m_fEnglish = english;
        m_strGrade = grade;
        cout << "Student(paragms..)...\n";
    }

    void info() const
    {
        Person::info();
        cout << "score: " << m_fMath 
             << ' ' << m_fChinese
             << ' ' << m_fEnglish
             << " 年级：" << m_strGrade << endl;
    }

private:
    float m_fMath;
    float m_fChinese;
    float m_fEnglish;
    string m_strGrade;
};
//多继承情况时，基类构造函数的调用顺序和继承顺序保持一致
//和在初始化列表中的前后顺序无关

//在虚继承情况下，由最派生类来真正继承被虚继承的类
//被虚继承的类中的成员的初始化由最派生类负责
class GraduateStudent: public Teacher, public Student
{
public:
    GraduateStudent(){}
    GraduateStudent(string id, string name
                    , int age, char sex, string addr
                    , float math, float chinese
                    , float english, string grade
                    , string courseName, float salary
                    , string level, string project)
        : Student(id, name, age, sex, addr
                  , math, chinese, english, grade)
          , Teacher(id, name, age, sex, addr
                    , courseName, salary)
          , Person(id, name, age, sex, addr)
    {
        m_strLevel = level;
        m_strProject = project;
        cout << "GraduateStudent(params...)\n";
    }
    void info() const
    {
        Student::info();
        Teacher::info();
            cout << m_strLevel << ' ' << m_strProject << endl;
    }
private:
    string m_strLevel;
    string m_strProject;
};

//person由Test真正继承
class Test: public GraduateStudent
{};

int main(void)
{
    GraduateStudent gs("1001", "xhangsan", 19
                       , 'f', "beijing", 90
                       , 98, 78, "二年级"
                       , "c++", 9000, "研究生"
                       , "机器自主学习");
    gs.info();
    cout << "person size:" << sizeof(Person) << endl;
    cout << "student size:" << sizeof(Student) << endl;
    cout << "teacher size:" << sizeof(Teacher) << endl;
    cout << "graduate size:" << sizeof(GraduateStudent) << endl;

    return 0;
}