C++ map with class pointer gives error while compiling

Question

I have a map with string and an class pointer. I am from JAVA so please guide me.

class Client {

public:
    static map<string, Client*> CLIENTS;
    Client(string dir);
    static Client* get_client(string name);
    virtual ~Client();
};

My get_client method is

Client* Client::get_client(string name) {
       map<string, Client*>::iterator it = CLIENTS.find(name);
}

gives me the error below

Undefined symbols for architecture x86_64:
  "Client::CLIENTS", referenced from:
      Client::get_client(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)in client.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

If your `get_client`'s body is exactly as you posted, then it's senseless — borisbn, Mar 16 '13 at 08:22
@borisbn i removed a lot of code while trying to locating the issue — Kathick, Mar 16 '13 at 09:06

Basile Starynkevitch · Accepted Answer · 2013-03-16T09:06:11.670

2

You need to define the CLIENTS which you have only declared. So outside of class Client{, in your clients.cpp file add

 std::map<std::string, Client*> Client::CLIENTS;

BTW, I find the name CLIENTS quite confusing. Maybe it should be client_dict

Don't forget to compile with debugging information and all warnings, e.g. with g++ -Wall -g on Linux. Improve your code till no warnings are given (your get_client will get some). And learn how to use the debugger (e.g. gdb on Linux).

edited Mar 16 '13 at 09:06

answered Mar 16 '13 at 08:15

Basile Starynkevitch

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I have added std::map CLIENTS; in the cpp file still i am getting same issue – Kathick Mar 16 '13 at 08:58
Sorry, that should be `client::CLIENTS` – Basile Starynkevitch Mar 16 '13 at 09:06

score 1 · Answer 2 · answered Mar 16 '13 at 08:18

1

Add

map<string, Client*> Client::CLIENTS;

to cpp file. And do not omit std:: prefix before STL classes. Especially in header

answered Mar 16 '13 at 08:18

borisbn

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C++ map with class pointer gives error while compiling

2 Answers2