在Firebreath项目中使用IBPP时发生LNK2019错误

Question

这就是我的问题。我正在Firebreath中编写web浏览器插件。插件必须根据客户端请求连接到不同的数据库（Firebird、MS SQL、My SQL等）。所以我正在创建一个类来管理到右DB的连接。为了连接到火鸟，我正在尝试使用IBPP。我设法在简单的测试项目中使用IBPP连接到FB。但现在，当我做一些更复杂的事情时，我遇到了这个奇怪的链接器错误LNK2019。

准确的错误消息是：

Error   2   error LNK2019: unresolved external symbol "class IBPP::Ptr<class IBPP::IDatabase>
__cdecl IBPP::DatabaseFactory(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)
" (?DatabaseFactory@IBPP@@YA?AV?$Ptr@VIDatabase@IBPP@@@1@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@000000@Z)
referenced in function "class IBPP::Ptr<class IBPP::IDatabase>
__cdecl IBPP::DatabaseFactory(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >
const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)"
(?DatabaseFactory@IBPP@@YA?AV?$Ptr@VIDatabase@IBPP@@@1@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@000@Z)
C:ff-extensionsF4UbuildprojectsF4UConvConnections.obj F4UConv

我的连接代码如下：
标题

#ifndef Connections_h
#define Connections_h
#include <cstdarg>
#include <string>
#include "ibppibpp.h"
#include "..LoggerLogger.h"
using namespace std;
namespace Connections{
    class Connection {
        public:
            void set_logger(Logger::Logger *logger);
            virtual bool setup_connection(string machine, string db_path, string login, string passwd)=0;
            virtual bool connect()=0;
            virtual bool disconnect()=0;
            virtual bool setup_statement(string sql_statement, const char *fmt, ...)=0;
            template <class Statement>
            Statement execute_statement();
        protected:
            string machine;
            string db_path;
            string login;
            string passwd;
            Logger::Logger *logger;
    };
    class FB_Connection : public Connection {
        public:
            ~FB_Connection();
            bool setup_connection(string machine, string db_path, string login, string passwd);
            bool connect();
            bool disconnect();
            bool setup_statement(string sql_statement, const char *fmt, ...);
            template <class Statement>
            Statement execute_statement();
        private:
            IBPP::Database db;
    };
};
#endif Connections_h

来源

#include "Connections.h"
namespace Connections{
    void Connection::set_logger(Logger::Logger *logger){
        this->logger = logger;
    }
    FB_Connection::~FB_Connection(){
        if(this->db->Connected()){
            this->disconnect();
        }
        db->Drop();
    }
    bool FB_Connection::setup_connection(string machine, string db_path, string login, string passwd){
        this->machine = machine;
        this->db_path = db_path;
        this->login = login;
        this->passwd = passwd;
        try{
            this->db = IBPP::DatabaseFactory(this->machine, this->db_path, this->login, this->passwd);
            this->db->Create(3);
        }catch(IBPP::Exception& e){
            if(logger != nullptr){
                this->logger->log(Logger::LogMsgValue[Logger::E_LOGMSG_000002]);
                this->logger->log(Logger::LEVEL_ERROR, e.ErrorMessage());
            }
            return false;
        }
        return true;
    }
    bool FB_Connection::connect(){
        return true;
    }
    bool FB_Connection::disconnect(){
        return true;
    }
    bool FB_Connection::setup_statement(string sql_statement, const char *fmt, ...){
        return true;
    }
    template <class Statement>
    Statement FB_Connection::execute_statement(){
        return this;
    }
}

我在谷歌上搜索了两天，仍然不知道出了什么问题。我理解LNK2019错误的含义，但不知道为什么会在这种情况下发生
生成此错误的行是：

this->db = IBPP::DatabaseFactory(this->machine, this->db_path, this->login, this->passwd);

有人能告诉我怎么了吗
哦，我正在使用Visual Studio 2012学习版。

Answer 1

您正试图访问源中的方法，而您尚未在连接namespace中提供该方法的定义，即

这种方法：

DatabaseFactory(this->machine, this->db_path, this->login, this->passwd);

在连接namespace中为其提供定义。

在源文件中写入using namespace connections;。