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 };
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
|
//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;} |
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
|
//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
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
|
#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
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
#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
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
|
#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：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
#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;} |
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
#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
本篇文章就到这里了，希望能够给你带来帮助，也希望您能够多多关注服务器之家的更多内容！
原文链接：https://blog.csdn.net/GiGi_Princess/article/details/120057308
