1.友元函数
2.友元类
3.继承（公有继承）
4.公有继承的访问权限
5.私有继承的访问权限
6.保护继承的访问权限（两次继承）
==友元函数==
#include <iostream>
using namespace std;
class love
{
public:
love(int you,int me);
friend int baby(love& );//################
private:
int Me;
int You;
};
love::love(int you,int me)
{
You = you;
Me = me;
}
int baby(love& refnum)
{
return refnum.You + refnum.Me ;//###########
}
int main()
{
love aini(500,21);
cout<<"我想对你说："<<baby(aini)<<endl;
return 0;
}
==友元类==
#include <iostream>
using namespace std;
class Date; //声明Date类
class Time //定义Time类，描述时分秒
{
public:
Time(int con_hour, int con_minute, int con_second) //定义构造函数
{
m_nHour = con_hour;
m_nMinute = con_minute;
m_nSecond = con_second;
}
friend class Date; //声明Date为Time的友元类
private:
int m_nHour, m_nMinute, m_nSecond;
};
class Date //定义Date类
{
public:
Date(int con_year, int con_month, int con_day)//定义构造函数
{
m_nYear = con_year;
m_nMonth = con_month;
m_nDay = con_day;
}
void display_date_time(Time &ref_time); //声明display_date_time()函数
private:
int m_nYear, m_nMonth, m_nDay;
};
/*
* 定义display_date_time()函数，显示年月日、时分秒信息。由于Date为Time类的友元类，
* 则Date中的函数为Time类的友元函数，可以访问Time类的私有成员，
* 这里直接访问了私有成员：m_nHour、m_nMinute、m_nSecond
*/
void Date::display_date_time(Time &ref_time)
{
cout << m_nYear << "-" << m_nMonth << "-" << m_nDay << " "
<< ref_time.m_nHour << ":" << ref_time.m_nMinute//################
<< ":" << ref_time.m_nSecond << endl; //###############
}
int main()
{
Time time(17, 30, 20); //定义Time对象
Date date(2017, 2, 23); //定义Date对象
date.display_date_time(time); //显示年月日、时分秒信息
return 0;
}
==继承（公有继承）==
#include <iostream>
#include <string>
using namespace std;
class Animal
{
public:
void speak()
{
cout<<"animal language."<<endl;
}
};
class Dog :public Animal //继承Animal的属性
{
public:
Dog (string con_name):m_Name(con_name){}
void print_name()
{
cout<<"con_name:"<<m_Name<<endl;
}
private:
string m_Name;
};
int main()
{
Dog dog("dogoo");
dog.speak(); //调用其继承的Animal属性里的speak函数
dog.print_name();
return 0;
}
==公有继承的访问权限==
#include <iostream>
#include <string>
using namespace std;
class Animal
{
public:
void set_weight(int weight){m_Weight = weight;}
int get_weight(){return m_Weight;}
void set_age(int age){m_Age = age;}
protected:
int m_Age; //protected成员可以被派生类访问
private:
int m_Weight; //私有成员被派生类不可访问
};
class Dog:public Animal
{
public:
Dog (string con_name):m_Name(con_name){}
void print_age(){ cout<<m_Name<<",age="<<m_Age<<endl; } //这里直接访问了//#################
private:
string m_Name;
};
int main()
{
Dog dog("dogoo");
dog.set_weight(6);
dog.set_age(8);
dog.print_age();
cout<<"weight ="<<dog.get_weight()<<endl; //这里通过继承基类成员函数输出weight值，不可直接访问
return 0;
}
==私有继承的访问权限==
//把从基类继承的protected、public成员当做私有成员，主函数不能直接访问基类的成员
#include <iostream>
#include <string>
using namespace std;
class Animal
{
public:
void set_weight(int weight){m_Weight = weight;}
int get_weight(){return m_Weight;}
void set_age(int age){ m_Age = age; }
protected:
int m_Age;
private:
int m_Weight;
};
class Dog:private Animal
{
public:
Dog(string con_name):m_Name(con_name){}
void set_print_weight()
{
set_weight(6); //################
cout<<m_Name<<",weight = "<<get_weight()<<endl;
}
void set_print_age()
{
set_age(8); //#################
cout<<m_Name<<",age = "<<m_Age<<endl;
}
private:
string m_Name;
};
int main()
{
Dog dog("dogoo");
dog.set_print_weight(); //通过派生类的访问来访问基类成员
dog.set_print_age();
return 0;
}
==保护继承的访问权限（多重继承：类Animal——>次类Dog——>再次类Dog_plus）==
//把从基类继承的protected、public成员当做保护成员
#include <iostream>
#include <stdlib.h>
#include <string>
using namespace std;
class Animal
{
public:
void set_weight(int weight){m_Weight = weight;}
int get_weight(){return m_Weight;}
void set_age(int age){m_Age = age;}
protected:
int m_Age;
private:
int m_Weight;
};
class Dog:protected Animal //#################
{
public:
Dog(string con_name):m_Name(con_name){}
void set_print_weight()
{
set_weight(8);
cout<<m_Name<<",weight ="<<get_weight()<<endl;
}
private:
string m_Name;
};
class plus_Dog:protected Dog //###################
{
public:
plus_Dog():Dog("dogoo"){ }
void plus_set_print_age()
{
set_age(6);
cout<<"The plus_dog age = "<<m_Age<<endl;
}
};
int main()
{
plus_Dog plus_dog;
plus_dog.plus_set_print_age();
system("pause");
return 0;
}