对象：一切都可为对象，类：相同特性的对象；面向对象特性：封装，继承，多态

一，封装

CLASS 类名 { 访问权限 ：属性/行为 }
实例化：通过一个类，创建一个对象

#include<iostream>
using namespace std;
#define PAI 3.14159

class  Circle //创建⚪类
{
public://访问权限：公共权限
	int m_r;//属性：半径
	double calculateZC()//行为：获取圆的周长，此用函数
	{
		return 2 * PAI * m_r;
	}
};
int main()
{
	Circle c1;//通过⚪类，创建对象
	c1.m_r = 10;//赋值
	cout << "⚪的周长为" << c1.calculateZC() << endl;
	return 0;
	system("pause");
}

属性+行为--》成员，属性——成员属性，成员变量；行为——成员函数，成员方法

#include<iostream>
using namespace std;
#define PAI 3.14159

class Student
{
public:
	string s_name;//属性
	int s_id;
	void showstudent()//行为
	{
		cout << "姓名\t" << s_name << endl;
		cout << "学号\t" << s_id << endl;
	}
	void setname(string name)
	{
		s_name = name;
	}
	void setid(int id)
	{
		s_id = id;
	}
};
int main()
{
	Student s1;
	s1.s_name = "王五";
	s1.s_id = 1242;
	s1.showstudent();

	/*cin >> s1.s_name >> s1.s_id;
	s1.showstudent();*/

	s1.setname("张三");
	s1.showstudent();
	s1.setid(78992342394);
	s1.showstudent();

	return 0;
	system("pause");
}

1.1 三种权限

类内外都可：PUBLIC ,
类内可，类外不可：PRIVATE （儿子可以访问父亲的保护内容）, PROTECTCED （儿子不可以访问父亲的私有内容）

#include<iostream>
using namespace std;
#define PAI 3.14159

class Person
{
public:
	string p_name;
protected:
	string p_car;
private:
	int p_password;

public:
	void func()//类内访问
	{
		p_name = "张三";
		p_car ="小米SU7";
		p_password = 4234235;
		cout << p_name << " " << p_car << " " << p_password << endl;
	}
};
int main()
{
	Person p1;
	p1.func();
	p1.p_name = "大哥";
	//p1.p_car = "小米SU7";类外不可访问
	//p1.p_password = 4234235;

	p1.func();
	//哈哈，运行这个函数就会赋值
	cout << p1.p_name << endl;
	p1.p_name = "大哥";
	cout << p1.p_name << endl;

	return 0;
	system("pause");
}

1.2 STRUCT 和 CLASS的区别

 STRUCT默认权限是公共，CLASS默认权限是私有

#include<iostream>
using namespace std;
#define PAI 3.14159

class P1//默认私有
{
	int m_a;
};
struct P2//默认公共
{
	int m_a;
};
int main()
{
	P1 pp1;
	//pp1.m_a = 3245;不可访问
	P2 pp2;
	pp2.m_a = 3245;
	return 0;
	system("pause");
}

1.3 成员属性设置为私有

优点：自己控制读写权限；对于写权限，可以检测数据的有效性

#include<iostream>
using namespace std;
#define PAI 3.14159

class P1//默认私有
{
public:
	void setname(string name)//设置NAME
	{
		m_name = name;
	}
	string getname()//读取NAME
	{
		return m_name;
	}
	int getage()
	{
		return m_age;
	}
	void settage(int age)
	{
		if (age < 0 || age>150)
		{
			cout << "年龄" << age << "数据有误，输入失败" << endl;
			return;
		}
		else
		{
			m_age = age;
		}
	}
	void setidol(string idol)
	{
		m_idol = idol;
	}
private:
	string m_name;//可读可写
	int m_age=18;//只读
	string m_idol;//只写
};

int main()
{
	P1 per1;
	per1.setname("拉拉");
	cout << per1.getname() << endl;

	//m_age = 20;
	//per1.setage(20);没有设置
	cout << per1.getage() << endl;
	per1.settage(900);
	cout << per1.getage() << endl;
	per1.settage(90);
	cout << per1.getage() << endl;

	per1.setidol("大大");
	//cout << per1.getidol("导弹无法去") << endl;没有设置

	return 0;
	system("pause");
}