Session, memory_store & NoMethodError

Hy everybody,

first, excuse me for my english, I'm french (sorry for that :D).

My actual problem is that I encountered a [b]NoMethodError[/b] when I
tried to access to a session value that is not nil. I'm doing some ajax
calls and I afffect the key/value and access to session variable in the
same controler "injection_controller.rb". I also access to session in a
view [b]_infos_fichiers_xml.html.erb[/b].

The access to session in the view [b]_infos_fichiers_xml.html.erb[/b]
does not cause any problem.
When I tried to access to the session in [b]injection_controller.rb[/b],
I get a :

[color=red][i]NoMethodError (You have a nil object when you didn't
expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.include?):[/i][/color]

The session contains an Array of objects "XmlFile" and I've configured
my environement.rb to use the memory store :
[i][b]config.action_controller.session_store = :memory_store[/b][/i]

This is my [b]injection_controller.rb[/b] session key/value affectation
code :
[code]def analysis_repository
      session[:list_xml] = create_XML_file_obj(false)#put an array of
XmlFile objects in the session
      render :update do |page|
         page[:liste_fichiers_xml].replace_html render(:partial =>

No error are generated when I access to session[:list_xml] from the view
[b]_infos_fichiers_xml.html.erb[/b] like this :
[code]<% session[:list_xml].each{|xml_file| %>
<% } %>"[/code]

But in an another method in [b]injection_controller.rb[/b] :
[code]def inject_data(name_xp,desc_xp)
    test = session[:list_xml]
    puts "#{test.nil?}"#this line print false
    test.each do|xml_file|#this line generate the error

So, it's very strange, and when I look at the session with <%= debug
session %> I can see the @data that contains my XmlFile array !

I probably do something bad ! :frowning:
I you have any ideas ?!

Thank you for advance !

Is this actually an array or an association proxy that looks like an
array ?


This is an array of objects, complete like this :

I only have the NoMethodError when accessing to the session key/value in
an another function than the one where affectation was made, but in the
same controler. Is it an envidence ?

If the problem only appears when accessing stuff put in the session by
a previous request and happens in development mode it's probably
related to code reloading. In between requests reloads your classes so
on subsequent requests your session contains objects of class that
rails has thrown out.

In general you should avoid sticking large or complicated things in
the session - for example you could store an array of ids of the
active record objects. You should also know that memory store isn't a
good choice for a production app - separate passenger or mongrel
instances won't share sessions


Ok, thanks a lot !

But, these objects are not already saved in the database, so I can not
save the ids !

I have to check a lot of things before doing that.........a solution
could be to use transactions.
How can I rollback after have saved objects ?

One more time, thank you Frederick !

Frederick Cheung wrote:

Ok, I have more informations :

I can read the array from session if I modify my development.rb file :
config.cache_classes = false
config.cache_classes = true

like in production. But of course, I have to restart the server each
times I modify my code to see the results.

Is it a cache bug in Rails ? Very strange !

It's a known side effect of the code reloading stuff, but as I said
above, the memory store is not going to be a good solution for
deployment so if I were you I'd try and find a way not to rely on it.


why topic starter, not use cookie store?

Ivan Nastyukhin

Because cookie store imply a strict size limit of 4kB......

Because cookie store imply a strict size limit of 4kB......

If you hitting that limit you are usually doing it wrong (database
sessions can contain larger objects though)


if u store models, at session - u are wrong

u should save, only ids to db, may be drafts, buts 4kb its normal for 99.8% situations

Ivan Nastyukhin