Re: [Cppcms-users] How to avoid "Access to unassigned context"

[Artyom B. <art...@ya...>]

Hello Marcel,


I'll explain,

what you are trying to do is to create a "User" class that is derived from cppcms::session
on the fly and then destroy it and this "User" object is not connected to the application.

cppcms::application objects are designed to be long-living objects. When a request
arrives and an application is selected from the pool it, and **all its children**
receive a cppcms::http::context, which holds the connection, session, request,
response. And once the request is complete, the context is destroyed and
the application object returns to the pool.

Now, what you are trying to do is to create an application on the fly,
and then destroy it. It is not the way to use application because
they should be either:

a) Stand alone application that are created from the pool 

   (assigned to the applications_pool() of the main service)
b) They are connected long living children of the application
   in the pool, sub-applications. In order to work properly
   they must be "added" or "attached" to the main application.
   

   It is usually done in the constructor of such application.
   Once they connected they share and use the same context.
   and they live together with this application as long as it
   lives.


So when you try to call user->session() you get an exception
as user does not know about the specific request context and 

is not connected to any application.


In your case User should not be derived from CppCMS application,
or it should be attached the same way to the Techtree the way
Techree is attached to Dispatcher.

I hope it makes it clear.

(I think this would be a good entry for wiki, if it is clear enough)
 
Best,


Artyom Beilis
--------------
CppCMS - C++ Web Framework:   http://cppcms.sf.net/
CppDB - C++ SQL Connectivity: http://cppcms.sf.net/sql/cppdb/


----- Original Message -----
> From: Marcel Hellwig <ke...@co...>
> To: cpp...@li...
> Cc: 
> Sent: Thursday, December 15, 2011 10:08 AM
> Subject: [Cppcms-users] How to avoid "Access to unassigned context"
> 
>G ood morning,
> 
> I'm writing a program that uses sessions. Here's my config:
> 
> "session" : {
>      "location" : "server",
>      "timeout" : 3600, //1 hour
>      "expire" : "renew",
>      "cookies" : {
> //    "domain" : "localhost",
>        "path"   : "/",
>        "prefix" : "bg_",
>        "secure" : false,
>      },
>      "server" : {
>        "storage" : "files",
>        "dir"      : "tmp/cookies",
>        "shared"  : false,
>      },
>      "gc" : 86400 //once a day
> },
> 
> now my problem.
> I'm using the dispatcher, there I assign the "fill" method, named 
> prepare. Everything works until now. In this "fill" method i declare a 
> 
> new pointer to an Object and give this pointer to an other method, named 
> "fillContent". There i use some methods from the 
> "pointed-Object". In 
> that object I have to, or I want to the session. That for the 
> Constructor of the Object becomes the cppcms::application reference.
> Now I try to set, or to read a cookie. Both fails with the error "Access 
> to unassigned context". If i remove that "session-line" 
> everything works 
> back to normal.
> 
> Please, give me some advices.
> 
> Regards,
> Marcel Hellwig
> Hamburg, Germany
> 
> 
> 
> Here some code:
> 
> Dispatcher::Dispatcher(cppcms::service &s) : cppcms::application(s) {
> .....
>      attach(new Techtree(s),
>             "Techtree",
>             "/techtree/{1}",
>             "/techtree/?(.*)", 1);
> .....
> }
> 
> Techtree::Techtree(cppcms::service& srv) : BasePage(srv) {
>      mapper().assign("{1}");
>      mapper().assign("");
>      dispatcher().assign(".*", &Techtree::prepare, this, 0);
> }
> 
> void Techtree::prepare(std::string /*page*/) {
>      User* user;
> ......
>      user = new User(_srv, session().get<int>("uID"));
> ......
>      session().set("uID", "1"); //this works!
> .....
>      fillContent(c, user); //c is the struct of template strings
>      delete user;
> }
> 
> void Techtree::fillContent(data::techtree::main c, User* user) {
> 
>      c.MetalMineDep = "<tr><td>---</td></tr>";
>      user->getBuildingLevel(101, 1);
>      c.SolarPowerPlantDep = 
> "<tr><td>---</td></tr>";
>      render("techtree", c);
> }
> 
> User::User(cppcms::service& srv, int id) : cppcms::application(srv),
>          _srv(srv), _userID(id) {
>      _conn_str = 
> _srv.settings().get<std::string>("bg.connection_string");
>      _sql.open(_conn_str);
>      _init();
> }
> 
> void User::_init() {
>    ........
>      session().set("test, "test123"); //here the error occurs
> }
> 
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