C++day4(拷贝赋值函数、匿名对象、友元、常成员函数和常对象、运算符重载)-编程知识

一、Xmind整理：

二、上课笔记整理：

1.day3作业订正：设计一个Per类，类中包含私有成员：姓名、年龄、指针成员身高...

#include <iostream>using namespace std;//封装人 类
class Person
{
private:string name;int age;double *h; //身高
public://无参构造函数Person() { cout << "Person::无参构造函数" << endl;}//有参构造Person(string name, int age , double h):name(name),age(age),h(new double(h))//h = new double(h){cout << "Person::有参构造函数" << endl;}//拷贝构造函数Person(const Person& p):name(p.name),age(p.age),h(new double(*(p.h))){cout << "Person::拷贝构造函数" << endl; }~Person(){cout << "Person::析构函数"  << endl;delete h;}};//封装学生 类
class Stu
{
private:int math;Person p;
public://Stu() {cout << "Stu::无参构造" << endl;}//Stu(string name, int age, double h, int math):math(math),p(name,age,h){cout << "Stu::有参构造" << endl;}//拷贝构造函数Stu(const Stu& s):math(s.math),p(s.p){cout << "Stu::拷贝构造函数" << endl;}~Stu(){cout << "Stu::析构函数"  << endl;}};int main()
{Stu s; //Stu s1("张三",34,189,67); //Stu s2 = s1;  //return 0;
}

2.封装学生的类，写出构造函数，析构函数、拷贝构造函数、拷贝赋值函数

#include <iostream>using namespace std;
class Stu
{
private:string name;int age;
public:Stu(){cout << "无参构造函数" << endl;}Stu(string name,int age):name(name),age(age){cout << "有参构造函数" << endl;}Stu(const Stu &other):name(other.name),age(other.age){cout << "拷贝构造函数" << endl;}Stu &operator=(const Stu &other){if(this != &other){name = other.name;age = other.age;cout << "拷贝赋值函数" << endl;}return *this;}~Stu(){cout << "析构函数"  << endl;}void display(){cout << name << endl;cout << age << endl;}
};int main()
{Stu s1 ("zhangsan",20);s1.display();Stu s2 =s1;s2.display();Stu s3;s3 = s2;s3.display();return 0;
}

3.匿名对象

#include <iostream>using namespace std;
class Stu
{
private:string name;int age;
public:Stu(){cout << "无参构造函数" <<endl;}Stu(string name,int age):name(name),age(age){cout << "有参构造函数" << endl;}void show(){cout << name << endl;cout << age << endl;}};
void fun(Stu s)
{s.show();
}int main()
{Stu s1 = Stu("zhangsan",12);s1.show();Stu s[3] = {Stu("a",1),Stu("b",2),Stu("c",3)};s[0].show();s[1].show();s[2].show();fun(Stu("lisi",5));return 0;
}

4.全局函数、类做友元

#include <iostream>using namespace std;
class Room
{friend void goodgay(Room &r);friend class GoodGay;
private:string mybedroom;
public:string livingroom;
public:Room(){mybedroom = "卧室";livingroom = "客厅";}
};//类做友元
class GoodGay
{
public:Room *r;void visit(){cout << "好基友类正在访问" << r->mybedroom <<endl;cout << "好基友类正在访问" << r->livingroom <<endl;}
public:GoodGay(){r = new Room;}
};//全局函数做友元
void goodgay(Room &r)
{cout << "好基友函数正在访问" << r.mybedroom <<endl;cout << "好基友函数正在访问" << r.livingroom <<endl;
}int main()
{Room r;goodgay(r);GoodGay g;g.visit();return 0;
}

5.成员函数做友元

#include <iostream>using namespace std;class Room;//声明有这样的类//类做友元
class GoodGay
{
public:Room *r;void visit();//在类内声明GoodGay();
};//封装 房间 类
class Room
{friend void GoodGay::visit();  //这个类的成员函数是本类的好朋友。可以访问本类所有成员
private:string m_BedRoom;  //卧室
public:string m_SittingRoom; //客厅
public://无参Room(){m_BedRoom = "卧室";m_SittingRoom = "客厅";}
};void GoodGay::visit()  //在类外定义成员函数
{cout << "好基友类正在访问。。" << r->m_SittingRoom << endl;cout << "好基友类正在访问。。"  << r->m_BedRoom << endl;
}
GoodGay::GoodGay()
{r = new Room;
}int main()
{GoodGay g;g.visit();return 0;
}

6.常成员函数

#include <iostream>using namespace std;class Stu
{
private:string name;int age;
public://无参构造函数Stu(){}//有参构造函数Stu(string name, int age):name(name),age(age){}//常成员函数void show()const{cout << "姓名：" << name << endl;cout << "年龄：" << age << endl;}
};int main()
{Stu s1("zhangsan",10);s1.show();return 0;
}

7.常对象+mutable关键字

#include <iostream>using namespace std;class Stu
{
private:string name;mutable int age;
public://无参构造函数Stu(){}//有参构造函数Stu(string name, int age):name(name),age(age){}//常成员函数void show()const{age = 19;cout << "姓名：" << name << endl;cout << "年龄：" << age << endl;}//非常成员函数void show(){age = 16;cout << "姓名：" << name << endl;cout << "年龄：" << age << endl;}
};int main()
{//非常对象Stu s1("zhangsan",10);s1.show();//常对象const Stu s2("lisi",15);s2.show();return 0;
}

8.实现+号运算符重载（成员函数、全局函数）

#include <iostream>using namespace std;class Person
{// friend const Person operator+(const Person &L, const Person &R);
private:int a;int b;
public://无参构造函数Person(){}//有参构造函数Person(int a, int b):a(a),b(b){}//成员函数实现 + 号运算符重载const Person operator+(const Person &R)const{Person temp;temp.a = a + R.a;temp.b = b + R.b;return temp;}void show(){cout << "a = " << a << endl;cout << "b = " << b << endl;}
};//全局函数实现 + 号运算符重载
//const Person operator+(const Person &L, const Person &R)
//{
//    Person temp;
//    temp.a = L.a + R.a;
//    temp.b = L.b + R.b;
//    return temp;
//}int main()
{Person p1(10,10);Person p2(10,10);Person p3 = p1 + p2;p3.show();return 0;
}