在 Firebreath 项目中使用 IBPP 时出现 LNK2019 错误

Question

所以这是我的问题。我正在 Firebreath 中编写网络浏览器插件。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）。所以我正在创建类来管理与正确数据库的连接。要连接到 Firebird，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。但是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。

确切的错误信息是：

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-extensions\F4U\build\projects\F4UConv\Connections.obj F4UConv

我的连接代码如下所示：
标题

#ifndef Connections_h
#define Connections_h

#include <cstdarg>
#include <string>

#include "ibpp\ibpp.h"
#include "..\Logger\Logger.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，仍然不知道是什么问题。我了解 LNK2019 错误的含义，但不知道为什么会出现这种情况。
产生此错误的行是：

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

谁能告诉我怎么了？
哦，我正在使用 Visual Studio 2012 Express。

Answer 1

您正在尝试访问未在连接namespace 中提供定义的源中的方法，即

这个方法：

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;。