C++类和对象之封装详解

目录

• 封装的意义以及示例
• 访问权限

• 公共权限 public
• 保护权限 protected
• 私有权限 private

#include<iostream>
using namespace std;
#define PI 3.14
class Circle
{
	//访问权限
	//公共权限
public:
	//属性
	int r;
	//行为
	double calculate()
	{
		return 2 * PI * r;
	}
};
int main()
{
	Circle a;
	a.r = 2;
	cout << a.calculate() << endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
class student
{
public:
	string name;
	int Id;
	void CinSudent()
	{
		cin >> name;
		cin >> Id;
	}
	void ShowStudent()
	{
		cout << name << endl;
		cout << Id << endl;
	}
};
int main()
{
	student a;
	a.CinSudent();
	a.ShowStudent();
	system("pause");
	return  0;
}

访问权限有三种：
1.public  公共权限
2.protected  保护权限
3.private   私有权限

class Box
{
   public:
      double length;
      void setWidth( double wid );
      double getWidth( void );
};

class Box
{
   protected:
      double length;
      void setWidth( double wid );
      double getWidth( void );
};

class Box
{
   private:
      double length;
      void setWidth( double wid );
      double getWidth( void );
};

#include<iostream>
using namespace std;
struct C1
{
	int m_A;//默认权限为公有
};
class C2
{
	int m_A;//默认权限为私有
};
int main()
{
	C1 c1;
	C2 c2;
	c1.m_A = 100;
	//c2.m_A = 100; 此处无法访问
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
class Person
{
public:
	void Setname(string name1)
	{
		name = name1;
	}
	string Showname()
	{
		return name;
	}
	int Showage()
	{
		return age;
	}
private:   //私有权限
	string name;
	int age=18;
};
int main()
{
	Person a;
	a.Setname("张三");
	cout << "姓名为： " << a.Showname() << endl;
	cout << "年龄为： " << a.Showage() << endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
class Cube
{
public:
	//设置长
	void setL(int l)
	{
		m_L = l;
	}
	//设置宽
	void setW(int w)
	{
		m_W = w;
	}
	//设置高
	void setH(int h)
	{
		m_H = h;
	}
	//获取长
	int getL()
	{
		return m_L;
	}
	//获取宽
	int getW()
	{
		return m_W;
	}
	//获取高
	int getH()
	{
		return m_H;
	}
	//获取面积
	int calculateS()
	{
		return 2 * (m_L * m_W + m_L * m_H + m_W * m_H);
	}
	//获取体积
	int calculateV()
	{
		return m_L * m_H * m_W;
	}
	//利用成员函数判断两个立方体是否相等
	bool isSameByClass(Cube& c)
	{
		if (m_H == c.getH() && m_L == c.getL() && m_W == c.getW())
			return true;
		else
			return false;
	}
private:
	int m_L;//长
	int m_W;//宽
	int m_H;//高
};
//利用全局函数判断两个立方体是否相等
bool isSame(Cube &c1,Cube &c2)
{
	if (c1.getH() == c2.getH() && c1.getL() == c2.getL() && c1.getW() == c2.getW())
		return true;
	else
		return false;
}
int main()
{
	Cube c1;
	c1.setH(10);
	c1.setL(13);
	c1.setW(45);
	cout << "c1面积是：" << c1.calculateS() << endl;
	cout << "c2体积是：" << c1.calculateV() << endl;
	Cube c2;
	c2.setH(10);
	c2.setL(13);
	c2.setW(45);
//利用全局函数判断
	if (isSame(c1, c2))
		cout << "c1和c2相等" << endl;
	else
		cout << "c1和c2不相等" << endl;
//利用成员函数判断
	if (c1.isSameByClass(c2))
		cout << "c1和c2相等" << endl;
	else
		cout << "c1和c2不相等" << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
class Point
{
public:
	//设置x
	void setX(int x)
	{
		m_X = x;
	}
	//设置y
	void setY(int y)
	{
		m_Y = y;
	}
	//获取x
	int  getX()
	{
		return m_X;
	}
	int getY()
	{
		return m_Y;
	}
private:
	int m_X;
	int m_Y;
};
class Circle
{
public:
	//设置半径
	void setR(int r)
	{
		m_R = r;
	}
	//获取半径
	int getR()
	{
		return m_R;
	}
	//设置圆心
	void setCenter(int x, int y)
	{
		m_Center.setX(x);
		m_Center.setY(y);
	}
	//获取圆心
	Point getCenter()
	{
		return m_Center;
	}
private:
	int m_R; //半径
	Point m_Center;//圆心
};
//判断点和圆的关系
void isInCircle(Circle& c, Point& p)
{
	//计算距离的平方
	int distance = (c.getCenter().getX() - p.getX()) * (c.getCenter().getX() - p.getX()) +
		           (c.getCenter().getY() - p.getY()) * (c.getCenter().getY() - p.getY());
	//计算半径的平方
	int RDistance = c.getR() * c.getR();
	//判断关系
	if (distance == RDistance)
		cout << "点在圆上" << endl;
	else if (distance > RDistance)
		cout << "点在圆外" << endl;
	else
		cout << "点在圆内" << endl;
}
int main()
{
	//创建一个圆
	Circle c;
	c.setR(10);
	c.setCenter(10, 0);
	Point p;
	p.setX(10);
	p.setY(10);
	//判断关系
	isInCircle(c,p);
	system("pause");
	return 0;
}