C++核心编程之类和对象详解

目录1.封装1.1封装的意义封装意义一：封装意义二1.2 struct 和 class 区别1.3 成员属性设置为私有总结

C++面向对象三大特性：封装、继承、多态

1.封装

1.1封装的意义 将属性和行为作为一个整体 将属性和行为加以权限控制

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 3.14class 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;}

1.2 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;}

1.3 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;}

总结

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泪，一种痛苦的雨滴，不知从什么时候开始已在我的世界下个不停。