Bidirectional link odb failed

Question

I have two classes with bidirectional link but the generation of odb files failed with this command :

odb --database mysql --generate-query --generate-schema --std c++14  -I./data-bdd/src/model *.hxx

I have this error (with MySQL and SQLite database type)

error: unable to map C++ type '::__gnu_cxx::new_allocator< ::std::weak_ptr< ::message > >::value_type' used in data member 'm_messages' to a MySQL database type
chat.hxx:29:39: info: use '#pragma db value_type' to specify the database type

I try to add pragma without effect

 #pragma db object pointer(std::shared_ptr)

Source files :

In chat.hxx

#include "./root_model_object.hxx"

 #include <memory>
 #include <string>
 #include <vector>

 class message;
 class user;

 /**
  * @brief class of chat object in model
  *
  */
 #pragma db object pointer(std::shared_ptr)
 class chat final : public root_model_object {
 private:
   friend class odb::access;
   std::string m_name;
 #pragma db value_not_null inverse(m_chat)
   std::vector<std::weak_ptr<message>> m_messages;
 #pragma db value_not_null inverse(m_chats)
   std::vector<std::weak_ptr<user>> m_members;

 public:
   /**
    * @brief Construct a new chat object
    *
    */
   chat() = default;

   /**
    * @brief Set the name of object
    *
    * @param name The name of object
    */
   void setName(const std::string &name) { m_name = name; };

   /**
    * @brief Get the name of object
    *
    * @return const std::string& the name of object
    */
   const std::string &getName() const { return m_name; };

   /**
    * @brief Set the messages of object
    *
    * @param messages The messages of object
    */
   void setMessages(const std::vector<std::weak_ptr<message>> &messages) {
     m_messages = messages;
   };

   /**
    * @brief Get the messages of object
    *
    * @return const std::vector<std::weak_ptr<message>>& the messages of object
    */
   const std::vector<std::weak_ptr<message>> &getMessages() const {
     return m_messages;
   };

   /**
    * @brief Set the members of object
    *
    * @param members The members of object
    */
   void setMembers(const std::vector<std::weak_ptr<user>> &members) {
     m_members = members;
   };

   /**
    * @brief Get the members of object
    *
    * @return const std::vector<std::weak_ptr<user>>& the members of object
    */
   const std::vector<std::weak_ptr<user>> &getMembers() const {
     return m_members;
   };
 };

 #pragma db object(chat)
 };

in message.hxx

#include "./chat.hxx"
 #include "./root_model_object.hxx"
 #include "./user.hxx"

 #include <ctime>
 #include <memory>
 #include <string>

 /**
  * @brief class of message object in model
  *
  */
 #pragma db object pointer(std::shared_ptr)
 class message final : public root_model_object {
 private:
   friend class odb::access;
   std::string m_content;
 #pragma db not_null
   std::shared_ptr<user> m_sender;
   std::time_t m_send_date;
 #pragma db not_null
   std::shared_ptr<chat> m_chat;

 public:
   /**
    * @brief Construct a new message object
    *
    */
   message() = default;

   /**
    * @brief Set the content of object
    *
    * @param content The content of object
    */
   void setContent(const std::string &content) { m_content = content; };

   /**
    * @brief Get the content of object
    *
    * @return const std::string& the content of object
    */
   const std::string &getContent() const { return m_content; };

   /**
    * @brief Set the sender of object
    *
    * @param sender The sender of object
    */
   void setSender(const std::shared_ptr<user> &sender) { m_sender = sender; };

   /**
    * @brief Get the sender of object
    *
    * @return const std::shared_ptr<user>& the sender of object
    */
   const std::shared_ptr<user> &getSender() const { return m_sender; };

   /**
    * @brief Set the send_date of object
    *
    * @param send_date The send_date of object
    */
   void setSendDate(const std::time_t &send_date) { m_send_date = send_date; };

   /**
    * @brief Get the send_date of object
    *
    * @return const std::time_t& the send_date of object
    */
   const std::time_t &getSendDate() const { return m_send_date; };

   /**
    * @brief Set the chat of object
    *
    * @param chat The chat of object
    */
   void setChat(const std::shared_ptr<chat> &chat) { m_chat = chat; };

   /**
    * @brief Get the chat of object
    *
    * @return const std::shared_ptr<chat>& the chat of object
    */
   const std::shared_ptr<chat> &getChat() const { return m_chat; };

 };

 #pragma db object(message)

Thanks a lot if you have the fix of this problem

Answer 1

When you do a forward declaration of an ORM class, you should tell the ODB compiler the definition of that class, like the following example.

• chat.hxx

#pragma once
...
class message;
...
#pragma db object ...
class chat ... {
...
    #pragma db ...
    std::vector<std::weak_ptr<message>> m_messages;
...
};

#ifdef ODB_COMPILER
#include "message.hxx"
#endif

See the reference for the detail.