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

[Marcel H. <ke...@co...>]

Hello Artyom,

I thank you for this great explanation. This makes some things clear.
It makes sense and I will costumize the User Class in that way.

Thanks again

Am 15.12.2011 10:08, schrieb Artyom Beilis:
> 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
>> }
>>
>> ------------------------------------------------------------------------------
>> 10 Tips for Better Server Consolidation
>> Server virtualization is being driven by many needs. 
>> But none more important than the need to reduce IT complexity
>> while improving strategic productivity.  Learn More!
>> http://www.accelacomm.com/jaw/sdnl/114/51507609/
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>>
> ------------------------------------------------------------------------------
> 10 Tips for Better Server Consolidation
> Server virtualization is being driven by many needs.
> But none more important than the need to reduce IT complexity
> while improving strategic productivity.  Learn More!
> http://www.accelacomm.com/jaw/sdnl/114/51507609/
> _______________________________________________
> Cppcms-users mailing list
> Cpp...@li...
> https://lists.sourceforge.net/lists/listinfo/cppcms-users