c++中的命名空间与静态成员函数的问题，问题解决

mikkoyue

1. 
   
2. $ vi socket.hpp
   
3.   1 #ifndef _MESSAGE_SOCKET_HPP
   
4.   2 #define _MESSAGE_SOCKET_HPP
   
5.   3
   
6.   4 #include <sys/types.h>
   
7.   5 #include <sys/socket.h>
   
8.   6
   
9.   7 namespace message_socket {
   
10.   8         class Socket
    
11.   9         {
    
12. 10         public:
    
13. 11                 Socket();
    
14. 12                 ~Socket();
    
15. 13
    
16. 14                 static void setDomain(int domain);
    
17. 15                 static void setType(int type);
    
18. 16                 static void setProtocol(int protocol);
    
19. 17
    
20. 18                 void debugPrint();
    
21. 19         private:
    
22. 20                 int _socket;
    
23. 21                 static int _domain;
    
24. 22                 static int _type;
    
25. 23                 static int _protocol;
    
26. 24         };
    
27. 25 }
    
28. 26 #endif
    
29. 
    

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1. 
   
2. $ vi socket.cpp
   
3.   1 #include "socket.hpp"
   
4.   2 #include <iostream>
   
5.   3
   
6.   4 using std::cout;
   
7.   5 using std::endl;
   
8.   6 using namespace message_socket;
   
9.   7
   
10.   8 Socket::Socket()
    
11.   9 {
    
12. 10         _socket = socket(_domain, _type, _protocol);
    
13. 11 }
    
14. 12
    
15. 13 Socket::~Socket()
    
16. 14 {
    
17. 15
    
18. 16 }
    
19. 17
    
20. 18 void Socket::setDomain(int domain)
    
21. 19 {
    
22. 20         _domain = domain;
    
23. 21 }
    
24. 22
    
25. 23 void Socket::setType(int type)
    
26. 24 {
    
27. 25         _type = type;
    
28. 26 }
    
29. 27
    
30. 28 void Socket::setProtocol(int protocol)
    
31. 29 {
    
32. 30         _protocol = protocol;
    
33. 31 }
    
34. 32
    
35. 33 void Socket::debugPrint()
    
36. 34 {
    
37. 35         cout << "_socket: " << _socket << endl;
    
38. 36         cout << "_domant: " << _domain << endl;
    
39. 37         cout << "_type: " << _type << endl;
    
40. 38         cout << "_protocol: " << _protocol << endl;
    
41. 39 }
    
42. 40
    

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1. 
   
2. $ vi test.cpp
   
3. #include "socket.hpp"
   
4. 
   
5. using namespace message_socket;
   
6. 
   
7. int main()
   
8. {
   
9.         Socket::setDomain(1);
   
10.         Socket::setType(2);
    
11.         Socket::setProtocol(0);
    
12. 
    
13.         Socket *sock = new Socket;
    
14. 
    
15.         sock->debugPrint();
    
16. 
    
17.         return 0;
    
18. }
    
19. 
    

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下面是编译时的错误信息

1. 
   
2. mikkoyue [ ~/cpp/message ]$ make
   
3. make  all-am
   
4. make[1]: Entering directory `/home/mikkoyue/cpp/message'
   
5. g++  -g -O2   -o testSocket test.o socket.o
   
6. socket.o: In function `message_socket::Socket::setDomain(int)':
   
7. /home/mikkoyue/cpp/message/socket.cpp:20: undefined reference to `message_socket::Socket::_domain'
   
8. socket.o: In function `message_socket::Socket::setType(int)':
   
9. /home/mikkoyue/cpp/message/socket.cpp:25: undefined reference to `message_socket::Socket::_type'
   
10. socket.o: In function `message_socket::Socket::setProtocol(int)':
    
11. /home/mikkoyue/cpp/message/socket.cpp:30: undefined reference to `message_socket::Socket::_protocol'
    
12. socket.o: In function `Socket':
    
13. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_protocol'
    
14. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_type'
    
15. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_domain'
    
16. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_protocol'
    
17. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_type'
    
18. /home/mikkoyue/cpp/message/socket.cpp:10: undefined reference to `message_socket::Socket::_domain'
    
19. socket.o: In function `message_socket::Socket::debugPrint()':
    
20. /home/mikkoyue/cpp/message/socket.cpp:36: undefined reference to `message_socket::Socket::_domain'
    
21. /home/mikkoyue/cpp/message/socket.cpp:37: undefined reference to `message_socket::Socket::_type'
    
22. /home/mikkoyue/cpp/message/socket.cpp:38: undefined reference to `message_socket::Socket::_protocol'
    
23. collect2: ld 返回 1
    
24. make[1]: *** [testSocket] 错误 1
    
25. make[1]: Leaving directory `/home/mikkoyue/cpp/message'
    
26. make: *** [all] 错误 2
    
27. mikkoyue [ ~/cpp/message ]$
    
28. 
    

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remote fish

static 属性 _domain, _type, _protocol 只有声明, 无定义.

解决方法:
在 socket.cpp 中加入以下行, 位置楼主请自行考虑

2. int Socket::_domain;
3. int Socket::_type;
4. int Socket::_protocol;

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mikkoyue

谢谢楼上的兄弟，问题解决