# Another sessions' persistence problem

**URL:** <https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175>\
**Category:** Rails\
**Created:** [October 15, 2006, 3:39am UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175 "2006-10-15T03:39:19Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 15, 2006, 3:39am UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/1 "2006-10-15T03:39:19Z")

</div>

Hi All,

I started out hashes intended to be populated with status info, e.g.  
sort\_order, for several of my tables. I started ApplicationController  
with:

```
session = {}
tables = [:customers, :invoices, :payments]
tables.each { |tbl| session[tbl] = {} }
session[:tables] = tables

```

Question 1: I had to include the initialization of session, for  
otherwise the assignment in the third line fails. But if Rails has a  
built-in ‘session’ hash-like element, why is this assignment  
necessary.

I checked that the above code worked by following it up with debugging  
code:

```
	logger.debug "Application tables:"
	nTables = session[:tables].length
	(0..(nTables-1)).each { |i|
		symTbl = session[:tables][i]
		objElement = session[symTbl]
		logger.debug "\t" + symTbl.to_s + " => " + objElement.inspect
	}

```

The log showed that the three empty hashes were indeed created.

I followed that up with a def show\_session defined with a copy of the  
debugging code. When this method was subsequently invoked by some  
other controller, it crashed on the second line because  
session[:tables] was nil … because session isn’t persistent, I  
believe.

Any ideas on how to correct this situation? I read the two recent  
threads about sessions, but they don’t seem to address my problem.

Thanks in Advance,  
Richard

---

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 15, 2006, 4:53am UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/2 "2006-10-15T04:53:31Z")

</div>

Hi~

On Oct 14, 2006, at 6:37 PM, Richard wrote:

> session[:tables] = tables  
> Is this inside of a method in your application controller? Or is it  
> just right in the class def? If its not inside of a method then the  
> session is not in scope. You shoudl do this with a before\_filter and  
> a method:

before\_filter :setup\_tables

def setup\_tables  
tables = [:customers, :invoices, :payments]  
tables.each { |tbl| session[tbl] = {} }  
session[:tables] = tables  
end

```
Then it should work for you.

```

-Ezra

---

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 15, 2006, 11:19pm UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/3 "2006-10-15T23:19:15Z")

</div>

Hi Ezra,

Your advice was a great boost forward. But I still have a problem.

BTW, I’m running:  
WinXP-Pro/SP2, MySQL 5.0.15-nt, Ruby 1.8.2-15, Rails 1.1.4  
SciTE 1.59, FireFox 1.2.0.7, Java JDK 1.5.0\_06

I used the before\_filter :setup\_tables, :show\_session That allowed my  
show\_session to method to work both upon entry and exit from the  
ApplicationController’s instantiation.

Show session also worked in app\controllers\MainController.rb#welcome

However, it failed in app\views\main\welcome.rhtml with the error:  
ActionView::TemplateError (undefined local variable or method  
`show\_session’

So I think I need to move it’s def to someplace higher than both  
controllers and views. How can I do that? Or should I make it a global  
function somehow?

If you don’t mind an additional question, please give me your  
assessment of a rescue clause I added to show\_session, as shown below.

Thanks for your outstanding advice.

Regards,  
Richard

class ApplicationController \< ActionController::Base  
before\_filter :setup\_tables, :show\_session  
layout “base”

```
logger.debug "==================================="
logger.debug "Entering app\\controllers\\application.rb (top level)"
logger.debug "==================================="

def setup_tables
	tables = [:customers, :invoices, :payments]
	tables.each { |tbl| session[tbl] = {} }
	session[:tables] = tables
end

def show_session
	logger.debug "Application tables:"
	nTables = session[:tables].length
	(0..(nTables-1)).each { |i|
		symTbl = session[:tables][i]
		objElement = session[symTbl]
		logger.debug "\t" + symTbl.to_s + " => " + objElement.inspect
	}
rescue
	raise "session[:tables] => nil" unless session[:tables]
	raise "nTables => #{nTables}" unless nTables != 3
	raise "symTbl => nil for session[:tables][#{i}]" unless symTbl
	raise "objElement => nil for session[#{symTbl}]" unless objElement
end

```

protected  
def sort\_clause(model, column, \*order)  
[snip]  
end

```
logger.debug "^^^^^^^^^^^^^^^^^^^^^^^"
logger.debug "Leaving app\\controllers\\application.rb (top level)"
logger.debug "vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv"

```

end

---

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 15, 2006, 11:33pm UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/4 "2006-10-15T23:33:18Z")

</div>

Hi~

On Oct 15, 2006, at 2:18 PM, Richard wrote:

> show\_session to method to work both upon entry and exit from the  
> global
> 
> ```
> tables.each { |tbl| session[tbl] = {} }
> }
> 
> ```
> 
> end
> 
> logger.debug “^^^^^^^^^^^^^^^^^^^^^^^”  
> logger.debug “Leaving app\controllers\application.rb (top level)”  
> logger.debug “vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv”  
> end

```
Lets rewrite some of this code to make it clearer.

```

class ApplicationController \< ActionController::Base

before\_filter :setup\_tables, :show\_session  
layout “base”

def setup\_tables  
tables = [:customers, :invoices, :payments].map{ |tbl| session  
[tbl] = {}; tbl }  
session[:tables] = tables  
end  
  
end

```
SO I think you can leave out the show_session method. And when you

```

want to see whats in the session in your view use this instead:

\<%= debug(session) %\>

```
That will show you everything that is currently in the session in a

```

nice yaml formatted view. If you really want to be able to call the  
show\_session method from a view then you can do that by useing  
helper\_method like this:

helper\_method :show\_session

put that in your application.rb class right after the definition of  
show\_session.

Cheers-

– Ezra Z.  
– Lead Rails Architect  
– removed\_email\_address@domain.invalid  
– Engine Y., Serious Rails Hosting  
– Reliability, Ease of Use, Scalability  
– (866) 518-YARD (9273)

---

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 16, 2006, 12:19am UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/5 "2006-10-16T00:19:24Z")

</div>

Hi Ezra,

Thanks again for your excellent suggestions:  
\<%= debug(session) %\> and  
helper\_method :show\_session

They’re nice to know. For the nonce, I want to stick with my  
show\_session because it focuses on the specific details I want from  
session. (OK, call me “stubborn”.)

And the good news (for me, anyway) is that I solved the scope problem,  
thanks to Rails For Ruby: I moved the def to  
app\helpers\application\_helper.rb

(By the way, I deleted my previous message because I was going to  
substitute the essential part of this message. Then I discovered your  
reply. This electronic correspondence is great!)

Again, many thanks for taking the time to look at (and solve!) my  
problem.

Best wishes,  
Richard

---

<div class="post-metadata">

**Author:** ![richard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f0a364/32.png) [@richard](https://www.ruby-forum.com/u/richard)\
**Post date:** [October 16, 2006, 4:32am UTC](https://www.ruby-forum.com/t/another-sessions-persistence-problem/72175/6 "2006-10-16T04:32:03Z")

</div>

This is just a test.