C++之高级编程

抽象：

纯虚函数：

1.virtual函数声明时后面加上 "=0"；

2.纯虚函数不需要定义

3.所有的纯虚函数都需要复写

1 #include <iostream>
 2 #include <string.h>
 3 #include <unistd.h>
 4 
 5 using namespace std;
 6 
 7 class Human{
 8 private:
 9     int a;
10 public:
11     virtual void eating(void) = 0;
12     virtual void wearing(void) = 0;
13     virtual void driving(void) = 0;
14     virtual ~Human() {cout <<"~Human()"<<endl;}
15     virtual Human *test (void){cout<<"Human's test"<<endl;return this;}
16     
17 };
18 class Englishman : public Human{
19 public:
20     void eating(void){cout<<"use knife to eat"<<endl;}
21     void wearing(void){cout<<"wear english style"<<endl;}
22     void driving(void){cout<<"drive english car"<<endl;}
23     virtual ~Englishman(){cout<<"~Englishman()"<<endl;}
24     virtual Englishman* test(void){cout<<"Englishman's test"<<endl;return this;}
25 
26 
27 };
28 class Chinese : public Human{
29 public:
30     void eating(void){cout<<"use chopsticks to eat"<<endl;}
31     void wearing(void){cout<<"wear chinese style"<<endl;}
32     //void driving(void){cout<<"drive chinese car"<<endl;} 
33     virtual ~Chinese(){cout<<"~Chinese()"<<endl;}
34     virtual Chinese* test(void){cout<<"Chinese's test"<<endl;return this;}
35 
36 };
37 class Guangximan : public Chinese{
38     //void driving(void){cout<<"drive chinese car"<<endl;} 
39 };
40 int main(int argc,char ** argv)
41 {
42     Englishman e;
43     Chinese c;
44 
45     return 0;
46 }

View Code

1 #include <iostream>
 2 #include <string.h>
 3 #include <unistd.h>
 4 
 5 using namespace std;
 6 
 7 class Human{
 8 private:
 9     int a;
10 public:
11     virtual void eating(void) = 0;
12     virtual void wearing(void) = 0;
13     virtual void driving(void) = 0;
14     virtual ~Human() {cout <<"~Human()"<<endl;}
15     virtual Human *test (void){cout<<"Human's test"<<endl;return this;}
16     
17 };
18 class Englishman : public Human{
19 public:
20     void eating(void){cout<<"use knife to eat"<<endl;}
21     void wearing(void){cout<<"wear english style"<<endl;}
22     void driving(void){cout<<"drive english car"<<endl;}
23     virtual ~Englishman(){cout<<"~Englishman()"<<endl;}
24     virtual Englishman* test(void){cout<<"Englishman's test"<<endl;return this;}
25 
26 
27 };
28 class Chinese : public Human{
29 public:
30     void eating(void){cout<<"use chopsticks to eat"<<endl;}
31     void wearing(void){cout<<"wear chinese style"<<endl;}
32     void driving(void){cout<<"drive chinese car"<<endl;} 
33     virtual ~Chinese(){cout<<"~Chinese()"<<endl;}
34     virtual Chinese* test(void){cout<<"Chinese's test"<<endl;return this;}
35 
36 };
37 int main(int argc,char ** argv)
38 {
39     Englishman e;
40     Chinese c;
41 
42     return 0;
43 }

View Code
此代码运行结果为下图：

抽象类：

1.含有纯虚函数的类

2.抽象类不能有实例对象

3.若子类没有覆写所有的纯虚函数，则子类还是抽象类

抽象类界面：

1.程序分为：应用编程、类编程

2.抽象类给应用编程提供固定的接口

3.具体类由抽象类派生出来

4.具体类编为动态库

优点:

应用编程、类编程互不影响

main中包含相对固定的.h文件，此.h文件也叫做接口,具体类应该有次而来。

app

Human.h

Englishman.h Chinese.h

1 #include "Human.h"
  2 //#include "Englishman.h"
  3 //#include "Chinese.h"
  4 
  5 void test_eating(Human *h)
  6 {
  7     h->eating();
  8 }
  9 
 10 
 11 int main(int argc, char **argv)
 12 {
 13     Human& e = CreateEnglishman("Bill", 10, "sfwqerfsdfas");//生成Englishman
 14     Human& c = CreateChinese("zhangsan", 11, "beijing");//生成Chinese
 15 
 16     Human* h[2] = {&e, &c};
 17     int i;
 18     for (i = 0; i < 2; i++)
 19         test_eating(h[i]);
 20 
 21     delete &e;
 22     delete &c;
 23     
 24     
 25     return 0;
 26 }
 27 main.cpp
 28 
 29 #ifndef _HUMAN_H
 30 #define _HUMAN_H
 31 
 32 #include <iostream>
 33 #include <string.h>
 34 #include <unistd.h>
 35 
 36 using namespace std;
 37 
 38 class Human {
 39 private:
 40     char *name;
 41 
 42 public:
 43     void setName(char *name);
 44     char *getName(void);
 45     virtual void eating(void) = 0;
 46     virtual void wearing(void) = 0;
 47     virtual void driving(void) = 0;
 48     virtual ~Human() {cout<<"~Human"<<endl;}
 49     
 50 };
 51 
 52 Human& CreateEnglishman(char *name, int age, char *address);
 53 Human& CreateChinese(char *name, int age, char *address);
 54 
 55 #endif
 56 Human.h
 57 
 58 #include "Human.h"
 59 
 60 void Human::setName(char *name) 
 61 {
 62     this->name = name;
 63 }
 64 
 65 char *Human::getName(void) 
 66 {
 67     return this->name;
 68 }
 69 Human.cpp
 70 
 71 #ifndef _ENGLISHMAN_H
 72 #define _ENGLISHMAN_H
 73 
 74 #include <iostream>
 75 #include <string.h>
 76 #include <unistd.h>
 77 
 78 #include "Human.h"
 79 
 80 using namespace std;
 81 
 82 class Englishman : public Human {
 83 private:
 84     char address[100];
 85     int age;
 86 public:
 87     void eating(void);
 88     void wearing(void);
 89     void driving(void);
 90     Englishman();
 91     Englishman(char *name, int age, char *address);
 92     virtual ~Englishman();
 93 };
 94 
 95 #endif
 96 English.h
 97 
 98 #include "Englishman.h"
 99 
100 
101 void Englishman::eating(void) 
102 { 
103     cout<<"use knife to eat"<<endl; 
104 }
105 
106 void Englishman::wearing(void) 
107 {
108     cout<<"wear english style"<<endl; 
109 }
110 
111 void Englishman::driving(void) 
112 {
113     cout<<"drive english car"<<endl; 
114 }
115 
116 Englishman::~Englishman() 
117 { 
118     cout<<"~Englishman()"<<endl; 
119 }
120 
121 Englishman::Englishman() {}
122 Englishman::Englishman(char *name, int age, char *address)
123 {
124     setName(name);
125     this->age = age;
126     memset(this->address, 0, 100);
127     strcpy(this->address, address);
128 }
129 
130 Human& CreateEnglishman(char *name, int age, char *address)
131 {
132     return *(new Englishman(name, age, address));
133 }
134 
135 English.cpp
136 
137 #ifndef _CHINESE_H
138 #define _CHINESE_H
139 
140 #include <iostream>
141 #include <string.h>
142 #include <unistd.h>
143 
144 #include "Human.h"
145 
146 using namespace std;
147 
148 class Chinese : public Human{
149 public:
150     void eating(void);
151     void wearing(void);
152     void driving(void);
153     virtual ~Chinese();
154 };
155 
156 #endif
157 
158 Chinese.h
159 
160 #include "Chinese.h"
161 
162 
163 void Chinese::eating(void) 
164 { 
165     cout<<"use chopsticks to eat"<<endl; 
166 }
167 
168 void Chinese::wearing(void) 
169 {
170     cout<<"wear chinese style"<<endl; 
171 }
172 
173 void Chinese::driving(void) 
174 {
175     cout<<"drive chinese car"<<endl; 
176 }
177 
178 Chinese::~Chinese() 
179 { 
180     cout<<"~Chinese()"<<endl; 
181 }
182 
183 Human& CreateChinese(char *name, int age, char *address)
184 {
185     return *(new Chinese());
186 }
187 Chinese.cpp
188 
189 Human: main.o libHuman.so
190     g++ -o $@ $< -L./ -lHuman
191 
192 %.o : %.cpp
193     g++ -fPIC -c -o $@ $<
194 
195 libHuman.so : Englishman.o Chinese.o Human.o
196     g++ -shared -o $@ $^
197 
198 clean:
199     rm -f *.o Human
200 Makefile

View Code
编译时使用本地库的命令：

LD_LIBRARY_PATH=./ ./Human
原文链接: https://www.cnblogs.com/yekongdebeijixing/p/12163788.html

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