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C++面向对象三大特性：封装、继承、多态
1.1 封装
1.1.1 封装的意义
封装意义一：
语法：class 类名{? 访问权限： 属性 / 行为 };? ? ? ? ? ? ? ?
//实例1
#define _CRT_SECURE_NO_WARNINGS 1
//求圆的周长
#include<iostream>
using namespace std;
#define pi 3.14
class circle
{
public:
int m_d;//直径
double calculate()
{
return pi*m_d;
}
};
int main()
{
circle c1;
c1.m_d = 10;
cout << "圆周长为" << c1.calculate() << endl;
system("pause");
return 0;
}
//实例2
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include <string>
class Student
{
public:
string m_name;
int m_num;
void showStudent()
{
cout << " 姓名：" << "\t" << m_name << " 学号：" << m_num << endl;
}
void setname(string name)
{
m_name = name;
}
void setnum(int num)
{
m_num = num;
}
};
int main()
{
Student s1;
s1.setname("zhangsan");
s1.setnum(2001);
s1.showStudent();
Student s2;
s2.setname("lisi");
s2.setnum(2002);
s2.showStudent();
system("pause");
return 0;
}
?总结：类中的 属性 和 行为 统一称为 成员
类中的 属性 又称为 成员属性 成员变量
类中的?行为?又称为 成员函数?成员方法
封装意义二
访问权限有三种
公共权限： public? ? ? ? ?成员类内可以访问，类外可以访问
保护权限： protected?? 成员类内可以访问，类外不可以访问? ? ?儿子可以访问父亲中的保护内容
私有权限： private? ? ? ?成员类内可以访问，类外不可以访问??儿子不可以访问父亲中的保护内容
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include <string>
class Student
{
public:
string m_name;
protected:
int m_num;
private:
int m_age;
public:
void func()
{
m_name = "lili";
m_num = 1;
m_age = 30;
}
private:
void func1()
{
m_name = "lili";
m_num = 1;
m_age = 30;
}
};
int main()
{
Student s1;
s1.m_name = "lilllll";
//s1.m_num = 2;//不可访问
//s1.m_age = 20;//不可访问
s1.func();
//s1.func1();//不可访问
system("pause");
return 0;
}
1.1.2 struct 和 class 区别
在C++中 struct 和 class 区别在于 默认的访问权限不同
- struct 默认权限为公共
- class 默认权限为私有
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
class C1
{
string m_a;
};
struct C2
{
string m_b;
};
int main()
{
//C1 c1;
//c1.m_a = "lili";//不可访问
C2 c2;
c2.m_b = "lili";
system("pause");
return 0;
}
1.1.3 成员属性设置为私有
优点：
- 将所有成员属性设置为私有，可以自己控制读写权限
- 对于写权限，我们可以检测数据的有效性
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class C1
{
public:
void setname(string name)
{
m_name = name;
}
string getname()
{
return m_name;
}
int getnum()
{
return m_num;
}
void setage(int age)
{
m_age = age;
}
private:
string m_name;
int m_num;
int m_age;
};
int main()
{
C1 c;
c.setname("yangyang");//可写
cout << c.getname() << endl;//可读
cout << c.getnum() << endl;//只读
c.setage(30);//只写
system("pause");
return 0;
}
好的，到这里封装就算是学到手了，可以进行两个小案例：
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class Cube
{
public:
void setchang(int chang)
{
m_c = chang;
}
void setkuan(int kuan)
{
m_k = kuan;
}
void setgao(int gao)
{
m_g = gao;
}
int getchang()
{
return m_c;
}
int getkuan()
{
return m_k;
}
int getgao()
{
return m_g;
}
int S()
{
return 2 * (m_c*m_g + m_c*m_k + m_g*m_k);
}
int V()
{
return m_c*m_g*m_k;
}
bool isSamebyclass(Cube &c)
{
if (m_c == c.getchang() && m_g == c.getgao() && m_k == c.getkuan())
{
return true;
}
return false;
}
private:
int m_c;
int m_k;
int m_g;
};
bool isSame1(Cube &c1, Cube &c2)
{
if (c1.getchang() == c2.getchang() && c1.getgao() == c2.getgao() && c1.getkuan() == c2.getkuan())
{
return true;
}
return false;
}
int main()
{
Cube c1;
c1.setchang(10);
c1.setkuan(10);
c1.setgao(10);
cout << "面积：" << c1.S() << endl;
cout << "体积：" << c1.V() << endl;
Cube c2;
c2.setchang(11);
c2.setkuan(11);
c2.setgao(11);
cout << "面积：" << c2.S() << endl;
cout << "体积：" << c2.V() << endl;
bool ret = isSame1(c1, c2);
if (ret)
{
cout << "全局函数判断：两个立方体相等" << endl;
}
else
{
cout << "全局函数判断：两个立方体不相等" << endl;
}
ret = c1.isSamebyclass(c2);
if (ret)
{
cout << "成员函数判断：两个立方体相等" << endl;
}
else
{
cout << "成员函数判断：两个立方体不相等" << endl;
}
system("pause");
return 0;
}
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class Point
{
public:
void setX(int x)
{
m_x = x;
}
int getX()
{
return m_x;
}
void setY(int y)
{
m_y = y;
}
int getY()
{
return m_y;
}
private:
int m_x;
int m_y;
};
class Circle
{
public:
void setR(int r)
{
m_r = r;
}
int getR()
{
return m_r;
}
void setcenter(Point center)
{
m_center = center;
}
Point getcenter()
{
return m_center;
}
private:
int m_r;
Point m_center;
};
void C_and_P(Circle &c, Point &p)
{
int distance = (c.getcenter().getX() - p.getX())*(c.getcenter().getX() - p.getX()) + (c.getcenter().getY() - p.getY())* (c.getcenter().getY() - p.getY());
int doubleR = c.getR()*c.getR();
if (distance==doubleR)
{
cout << "点在圆上" << endl;
}
else if (distance<doubleR)
{
cout << "点在圆内" << endl;
}
else
{
cout << "点在圆外" << endl;
}
}
int main()
{
Point p;
p.setX(10);
p.setY(30);
Circle c;
c.setR(10);
Point center;
center.setX(26);
center.setY(43);
C_and_P(c, p);
system("pause");
return 0;
}
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