cpp：类中的静态成员变量和静态成员函数（class）

一、类中的静态成员变量和静态成员函数：

　　1、类中的静态成员变量和静态成员函数：它们属于‘类’不属于‘对象’，它们没有指针‘ this ’。

　　2、类中的静态成员变量和静态成员函数：静态成员变量，只能在类外初始化；静态成员函数只能访问静态成员变量、静态成员函数以及与本类无关的函数；

　　3、伪代码：

 1 #include<iostream>
 2 
 3 
 4 using namespace std;
 5 
 6 
 7 class information
 8 {
 9 public:
10         information(){ count++;}
11         information(int e){ count++; elem=e;}
12         ~information(){ cout << "OS: ~information()" << endl; }
13         void set(int e){elem=e;}
14         int get(){ return elem;}
15         void print_count()
16         {
17                 // using static member count 
18                 cout << "print_count = " << count << endl;
19         }
20         static void msg();
21         static void count_object();
22 private:
23         int elem;
24         static int count; 
25 };
26 
27 
28 // define static function msg(); no keyword 'static'
29 void information::msg()
30 {
31         cout <<"\nvoid information::msg()\n" << endl;
32 }
33 
34 
35 // define static function count_object(), no keyword 'static'
36 void information::count_object()
37 {
38         // first: using static count 
39         // cout << "\ninformation_object = " << information::count << "\n" << endl;
40 
41         // second: using static count 
42         cout << "\ninformation_object = " << count << "\n" << endl;
43 }

二、应用示例

  1 [root@rockylinux tmp]# cat static_member_function_class.cpp 
  2 #include<iostream>
  3 
  4 
  5 using namespace std;
  6 
  7 
  8 class information
  9 {
 10 public:
 11         information(){ count++;}
 12         information(int e){ count++; elem=e;}
 13         ~information(){ cout << "OS: ~information()" << endl; }
 14         void set(int e){elem=e;}
 15         int get(){ return elem;}
 16         void print_count()
 17         {
 18                 // using static member count 
 19                 cout << "print_count = " << count << endl;
 20         }
 21         static void msg();
 22         static void count_object();
 23 private:
 24         int elem;
 25         static int count; 
 26 };
 27 
 28 
 29 // define static function msg(); no keyword 'static'
 30 void information::msg()
 31 {
 32         cout <<"\nvoid information::msg()\n" << endl;
 33 }
 34 
 35 
 36 // define static function count_object(), no keyword 'static'
 37 void information::count_object()
 38 {
 39         // first: using static count 
 40         // cout << "\ninformation_object = " << information::count << "\n" << endl;
 41 
 42         // second: using static count 
 43         cout << "\ninformation_object = " << count << "\n" << endl;
 44 }
 45 
 46 
 47 // static variable initial; no keyword 'static'
 48 int information::count = 0;
 49 
 50 
 51 // using static member function
 52 void use_static_member_function()
 53 {
 54         // using static member function
 55         information::count_object();
 56 }
 57 
 58 
 59 // create information object , oject number is 'size'. 
 60 information* create_information_object(int size)
 61 {
 62         information* pointer_information;
 63         information object_array[size];
 64         pointer_information = object_array;
 65 
 66         return pointer_information;
 67 }
 68 
 69 
 70 // use the function 'print_count()' of an object array of information.
 71 void use_information_object(information* pointer_information, int size)
 72 {
 73         cout <<"\n"<< endl;
 74         for(int i=0; i<size; i++)
 75         {
 76                 pointer_information -> print_count();
 77                 pointer_information++;
 78         }
 79         cout <<"\n"<< endl;
 80 
 81 }
 82 
 83 
 84 // test part.
 85 int main(int argc, char* argv[], char* envp[])
 86 {
 87 
 88         // print count, when it initializes.
 89         // information::count_object();
 90         use_static_member_function();
 91 
 92         // information create 10 objects.
 93         information* ptinfo ;
 94         ptinfo = create_information_object(10);
 95         use_information_object(ptinfo, 10);
 96 
 97         // print count, after information creates 10 ojects.
 98         // information::count_object();
 99         use_static_member_function();
100 
101         return 0;
102 }
103 [root@rockylinux tmp]# 
104 [root@rockylinux tmp]# 
105 [root@rockylinux tmp]# ./static_member_function_class 
106 
107 information_object = 0
108 
109 OS: ~information()
110 OS: ~information()
111 OS: ~information()
112 OS: ~information()
113 OS: ~information()
114 OS: ~information()
115 OS: ~information()
116 OS: ~information()
117 OS: ~information()
118 OS: ~information()
119 
120 
121 print_count = 10
122 print_count = 10
123 print_count = 10
124 print_count = 10
125 print_count = 10
126 print_count = 10
127 print_count = 10
128 print_count = 10
129 print_count = 10
130 print_count = 10
131 
132 
133 
134 information_object = 10
135 
136 [root@rockylinux tmp]# 
137 [root@rockylinux tmp]#

posted on 2022-09-03 18:00 lnlidawei 阅读(412) 评论(0) 编辑收藏举报

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