queue of structure with template argument

[michaelD]

Hello everyone,

I have an issue with a queue of structure which contain a template variable.

This is my code :

template <typename data_request> //Création d'un type data_request qui va contenir toute les données des structures utilisées
//!
//!\struct request_JSON
//!\detail structure for request sent to WEB_server
//! this structure is used to store request data information of data synchronized
//!
struct request_JSON{
string unique_number = "";
string request_type = "";
data_request *data;
};

queue<request_JSON<data_request>> sync_queue;


And my error is :

Video_Manager/../Commun/inc/../structuretype.hpp:465:20: error: 'data_request' was not declared in this scope
queue<request_JSON<data_request>> sync_queue;
^
Video_Manager/../Commun/inc/../structuretype.hpp:465:20: error: template argument 1 is invalid
Video_Manager/../Commun/inc/../structuretype.hpp:465:32: error: template argument 1 is invalid
queue<request_JSON<data_request>> sync_queue;
^
Video_Manager/../Commun/inc/../structuretype.hpp:465:32: error: template argument 2 is invalid
In file included from Video_Manager/../Commun/manager.hpp:5:0,
from Video_Manager/video_manager.hpp:4,
from main.cpp:11:

Does anyone have an idea ?

[coder777]

You need to provide a concrete data type like int:

queue<request_JSON<int>> sync_queue;

[Repeater]

queue<request_JSON<data_request>> sync_queue;

It's a template. When you create an actual object, you have to say what actual type you're using.

Try queue<request_JSON<int>> sync_queue; , for example

[michaelD]

Thanks for your response.

I understand I had to specify the type of the variable I used but I need to have different structure in data_request.

It is possible ?

My objective is to use a queue of different structure. each data_request structure can be identify by the request_type. And I had to do specific treatment on each structure.

[coder777]

A container like queue can have only one type. You can however store pointers. E.g.:

struct request{
string unique_number = "";
string request_type = "";
};

template <typename data_request> //Création d'un type data_request qui va contenir toute les données des structures utilisées
//!
//!\struct request_JSON
//!\detail structure for request sent to WEB_server
//! this structure is used to store request data information of data synchronized
//!
struct request_JSON : request{
data_request *data;
};

queue<std::unique_ptr<request>> sync_queue;

[michaelD]

Thank you for your response.

I think I find another way to do what I want.

//!
//!\struct request_JSON
//!\detail structure for request sent to WEB_server
//! this structure is used to store request data information of data synchronized
//!
struct request_JSON{
string unique_number = "";
string request_type = "";
string data = "";
};

queue<request_JSON> sync_queue;

where data is a string of my JSON object formated before push in the queue. With this solution I have always a string type.

What do you think about this ?

[coder777]

The simplest approach is usually the best.