Rails - Feb 2006 - Session magic question

Greetings!

I could really use some help understanding what Rails puts into the session
store related to the objects it creates.  I''ve found documentation on
how _I_ can put / get info into it, but can''t find the docs on what
_Rails_ puts into it.

I''ve got a simple app that collects some data from the user, stores it
in a db record, allows the user to edit it, display it, and save it to an XML
file.  Right now it''s real simple: 1 table.

I want the user to be able to create one and only one record in that table
during a session.  There''s a menu item that lets the user enter and /
or edit the data in that record.  The first time they select that item they get
a blank form, fill it in, and save it.  If they select that item again, the
request gets redirected to the ''edit'' action and they get a
form with the existing data displayed.  I figure to check the session to see if
there''s an entry for that object (like the Cart object in the Depot
app) to drive the logic.  I''m assuming this will work, but....

Can someone point me to some documentation on just exactly what Rails is putting
into the session store, how to access it, etc?

Thanks,
Bill
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Hello,

Rails don''t put anything in session relative to database access.

You have to deal with your oneshoot insert in the database.

That''s quickly what I''ve in mind regarding to your needs. You
can also
look near before_insert filter, and other filters or validation.

def save
   @session[:tracker] ||= 1  # initialize that session key at 1 if not
allready defined
   if @session[:tracker]==1
       don''t save, redirect to home
   end
   really save
end

Cheers,

Hi Mathieu,

Thanks for the quick reply.  I''m a little confused, I think. 
I''ve got a
model Class named ''emrec''.  It''s an AR class based on
the ''emrecs'' table so,
yeah, it''s got to do with the database.  But I thought that when I
created
''@emrec = Emrec.new'' that Rails put an entry for that object
into the
session hash.  I thought, further, that I could find out whether or not the
object already existed by checking to see if there was an entry for it in
the session hash (e.g., @emrec = session[:emrec] ||= Emrec.new).  No?

Thanks,
Bill

----- Original Message -----
From: "Mathieu Chappuis" <mathieu.chappuis.lists@gmail.com>
To: <rails@lists.rubyonrails.org>
Sent: 2006-02-28 8:53 AM
Subject: Re: [Rails] Session magic question


Hello,

Rails don''t put anything in session relative to database access.

You have to deal with your oneshoot insert in the database.

That''s quickly what I''ve in mind regarding to your needs. You
can also
look near before_insert filter, and other filters or validation.

def save
   @session[:tracker] ||= 1  # initialize that session key at 1 if not
allready defined
   if @session[:tracker]==1
       don''t save, redirect to home
   end
   really save
end

Cheers,
_______________________________________________
Rails mailing list
Rails@lists.rubyonrails.org
http://lists.rubyonrails.org/mailman/listinfo/rails

No... I don''t think anything gets put in the session unless you put it
there (and you have
to remove it too).

b

Bill Walton wrote:
> Hi Mathieu,
> 
> Thanks for the quick reply.  I''m a little confused, I think. 
I''ve got a
> model Class named ''emrec''.  It''s an AR class
based on the ''emrecs'' table so,
> yeah, it''s got to do with the database.  But I thought that when I
created
> ''@emrec = Emrec.new'' that Rails put an entry for that
object into the
> session hash.  I thought, further, that I could find out whether or not the
> object already existed by checking to see if there was an entry for it in
> the session hash (e.g., @emrec = session[:emrec] ||= Emrec.new).  No?
> 
> Thanks,
> Bill
> 
> ----- Original Message -----
> From: "Mathieu Chappuis" <mathieu.chappuis.lists@gmail.com>
> To: <rails@lists.rubyonrails.org>
> Sent: 2006-02-28 8:53 AM
> Subject: Re: [Rails] Session magic question
> 
> 
> Hello,
> 
> Rails don''t put anything in session relative to database access.
> 
> You have to deal with your oneshoot insert in the database.
> 
> That''s quickly what I''ve in mind regarding to your needs.
You can also
> look near before_insert filter, and other filters or validation.
> 
> def save
>    @session[:tracker] ||= 1  # initialize that session key at 1 if not
> allready defined
>    if @session[:tracker]==1
>        don''t save, redirect to home
>    end
>    really save
> end
> 
> Cheers,
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

Hi Ben,

Thanks for the reply.  If what you say is true, then I really don''t
understand how the shopping cart functionality in the Depot application
works.  On p.81 of AWD the implementation of the find_cart method is:

def find_cart
  session[:cart] ||= Cart.new
end

It''s explained as follows...

"If the session hash has a value corresponding to the key
'':cart'', that
value is returned immediately.  Otherwise a new cart object is created and
assigned to the session.  This new cart is then returned."

I assumed ''Cart.new'' did the assignment to the session.  If
not, how''s it
done?  There''s no place anywhere in the app that I can find that does
an
explicit assignment of the Cart object id to the session.  Help, please
?!?!?!? ;-)

Thanks,
Bill


----- Original Message -----
From: "Ben Munat" <bent@munat.com>
To: <rails@lists.rubyonrails.org>
Sent: 2006-02-28 11:01 AM
Subject: Re: [Rails] Session magic question

> No... I don''t think anything gets put in the session unless you
put it
there (and you have
> to remove it too).
>
> b
>
> Bill Walton wrote:
> > Hi Mathieu,
> >
> > Thanks for the quick reply.  I''m a little confused, I think. 
I''ve got a
> > model Class named ''emrec''.  It''s an AR
class based on the ''emrecs'' table
so,
> > yeah, it''s got to do with the database.  But I thought that
when I
created
> > ''@emrec = Emrec.new'' that Rails put an entry for
that object into the
> > session hash.  I thought, further, that I could find out whether or
not
the
> > object already existed by checking to see if there was an entry for it
in
> > the session hash (e.g., @emrec = session[:emrec] ||= Emrec.new).  No?
> >
> > Thanks,
> > Bill
> >
> > ----- Original Message -----
> > From: "Mathieu Chappuis"
<mathieu.chappuis.lists@gmail.com>
> > To: <rails@lists.rubyonrails.org>
> > Sent: 2006-02-28 8:53 AM
> > Subject: Re: [Rails] Session magic question
> >
> >
> > Hello,
> >
> > Rails don''t put anything in session relative to database
access.
> >
> > You have to deal with your oneshoot insert in the database.
> >
> > That''s quickly what I''ve in mind regarding to your
needs. You can also
> > look near before_insert filter, and other filters or validation.
> >
> > def save
> >    @session[:tracker] ||= 1  # initialize that session key at 1 if not
> > allready defined
> >    if @session[:tracker]==1
> >        don''t save, redirect to home
> >    end
> >    really save
> > end
> >
> > Cheers,
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

On Feb 28, 2006, at 11:47 AM, Bill Walton wrote:
>   session[:cart] ||= Cart.new
>
> I assumed ''Cart.new'' did the assignment to the session. 
If not,
> how''s it
> done?  There''s no place anywhere in the app that I can find that  
> does an
> explicit assignment of the Cart object id to the session.  Help,  
> please

session[:cart] ||= Cart.new

is the same as

session[:cart] = session[:cart] || Cart.new

There''s an assignment in there :)


Dave

I''m not Ben, but I can answer this one fairly easily...

The piece that you are missing with your example from AWD is the fact 
that the Cart model object isn''t an Active Record object. It''s
simply a
class defined within app/models, used to hold a hash object that 
contains the shopping cart items. A brand new Cart object is being 
stored in the session (if it doesn''t already exist) in the find_cart
method.

-Brian

Bill Walton wrote:
> Thanks for the reply.  If what you say is true, then I really
don''t
> understand how the shopping cart functionality in the Depot application
> works.  On p.81 of AWD the implementation of the find_cart method is:
> 
> def find_cart
>   session[:cart] ||= Cart.new
> end
> 
> It''s explained as follows...
> 
> "If the session hash has a value corresponding to the key
'':cart'', that
> value is returned immediately.  Otherwise a new cart object is created and
> assigned to the session.  This new cart is then returned."
> 
> I assumed ''Cart.new'' did the assignment to the session. 
If not, how''s it
> done?  There''s no place anywhere in the app that I can find that
does an
> explicit assignment of the Cart object id to the session.  Help, please
> ?!?!?!? ;-)
> 
> Thanks,
> Bill

Hi Brian,

Brian V. Hughes wrote:
>
> I''m not Ben, but I can answer this one fairly easily...
>
> The piece that you are missing with your example from AWD is the fact
> that the Cart model object isn''t an Active Record object.
It''s simply a
> class defined within app/models, used to hold a hash object that
> contains the shopping cart items. A brand new Cart object is being
> stored in the session (if it doesn''t already exist) in the
find_cart
method.

Are you saying that, if the Cart object was _not_ an AR object, that it (or
it''s ID I guess) would _not_ be stored in the session?

Sorry I''m being so dense on this.  Thanks for your help!

Best regards,
Bill

Hi Dave,

Dave Thomas wrote:
>
> session[:cart] ||= Cart.new
>
> is the same as
>
> session[:cart] = session[:cart] || Cart.new
>
> There''s an assignment in there :)
So the Cart.new method _does_ put the Cart id value in the session store?
Does ''.new'' do that for _all_ new objects?  What does it do
for the second,
third, etc. instance of that Class?  Do I end up with something like @carts
= session[:cart.each]?  I hate to keep asking these nuby questions and will
be very happy to go away and study the documentation if you''ll point me
to
it.

Thanks!
Bill

> So the Cart.new method _does_ put the Cart id value in the session store?
No Bill, you are wrong here, it is the "=" in: "session[:cart] =
Cart.new"
who stores that new cart instance in the session.




----- Original Message ----- 
"Bill Walton wrote:
> Hi Dave,
>
> Dave Thomas wrote:
>>
>> session[:cart] ||= Cart.new
>>
>> is the same as
>>
>> session[:cart] = session[:cart] || Cart.new
>>
>> There''s an assignment in there :)
>
> So the Cart.new method _does_ put the Cart id value in the session store?
> Does ''.new'' do that for _all_ new objects?  What does it
do for the
> second,
> third, etc. instance of that Class?  Do I end up with something like 
> @carts
> = session[:cart.each]?  I hate to keep asking these nuby questions and 
> will
> be very happy to go away and study the documentation if you''ll
point me to
> it.
>
> Thanks!
> Bill

Bill Walton wrote:
> Are you saying that, if the Cart object was _not_ an AR object, that it (or
> it''s ID I guess) would _not_ be stored in the session?
I believe the answer is yes, but you''ve got several extra negatives in 
there. ;)

To be more clear, I''m not sure you''d want to store an entire
AR object
in the session hash. If you need to carry around easy access to an AR 
object, request to request, then I would simply store the ID: 
session[:foo_id] = foo.id (where foo is an AR object.
> Sorry I''m being so dense on this.  Thanks for your help!
Not a problem. This stuff can be a little confusing.

-Brian

Hi again,

Dave Thomas wrote:
>
> session[:cart] ||= Cart.new
>
> is the same as
>
> session[:cart] = session[:cart] || Cart.new
>
> There''s an assignment in there :)
Ah (he says wishing he hadn''t responded so quickly earlier ;-p )

So Cart.new returns the object id which gets passed through the assignment
operator to session[:cart].

Maybe what''s throwing me it that the documentation on the Rails wiki
(http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
assignments being done to what I thought was an instance variable:

@session[:greeting] = "Hello world!"

How come the Depot app doesn''t need to use @session[] instead of
session[]
to store the Cart id?

Maybe I''m confused on local vs. instance variables?

Thanks,
Bill

On Feb 28, 2006, at 10:35 AM, Bill Walton wrote:
> Dave Thomas wrote:
>>
>> session[:cart] ||= Cart.new
>>
>> is the same as
>>
>> session[:cart] = session[:cart] || Cart.new
>>
>> There''s an assignment in there :)
>
> Ah (he says wishing he hadn''t responded so quickly earlier ;-p )
>
> So Cart.new returns the object id which gets passed through the  
> assignment
> operator to session[:cart].
Cart.new doesn''t return the object id, it returns the object itself.

-- 
-- Tom Mornini

On Feb 28, 2006, at 12:35 PM, Bill Walton wrote:
> Maybe what''s throwing me it that the documentation on the Rails
wiki
> (http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
> assignments being done to what I thought was an instance variable:
>
> @session[:greeting] = "Hello world!"
>
> How come the Depot app doesn''t need to use @session[] instead of  
> session[]
> to store the Cart id?
>
> Maybe I''m confused on local vs. instance variables?

The wiki''s out of date. Both work, but session[] is preferred over  
@session.

Dave

On 2/28/06, Bill Walton <bill.walton@charter.net>
wrote:
> So Cart.new returns the object id which gets passed through the assignment
> operator to session[:cart].
>
> Maybe what''s throwing me it that the documentation on the Rails
wiki
> (http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
> assignments being done to what I thought was an instance variable:
>
> @session[:greeting] = "Hello world!"
>
> How come the Depot app doesn''t need to use @session[] instead of
session[]
> to store the Cart id?
>
> Maybe I''m confused on local vs. instance variables?

Based on your questions, and that you really seem to want to learn
this, I''d recommend Ruby for Rails.  It''s in beta right now,
but the
available PDF chapters already cover a lot of what you''re asking about
here.

http://www.manning.com/books/black

> On 2/28/06, Bill Walton <bill.walton@charter.net> wrote:
>> So Cart.new returns the object id which gets passed through the  
>> assignment
>> operator to session[:cart].
>>
>> Maybe what''s throwing me it that the documentation on the
Rails wiki
>> (http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
>> assignments being done to what I thought was an instance variable:
>>
>> @session[:greeting] = "Hello world!"
>>
>> How come the Depot app doesn''t need to use @session[] instead
of
>> session[]
>> to store the Cart id?
>>
>> Maybe I''m confused on local vs. instance variables?
No, you''re confused because there''s two ways to do it.

And, it''s an instance variable (@session) -vs- a method call (session 
[]) in
this case, I believe.

--
-- Tom Mornini

At 2/28/2006 01:53 PM, you wrote:
>On Feb 28, 2006, at 12:35 PM, Bill Walton wrote:
>
>>Maybe what''s throwing me it that the documentation on the Rails
wiki
>>(http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
>>assignments being done to what I thought was an instance variable:
>>
>>@session[:greeting] = "Hello world!"
>>
>>How come the Depot app doesn''t need to use @session[] instead
of
>>session[]
>>to store the Cart id?
>>
>>Maybe I''m confused on local vs. instance variables?
>
>
>The wiki''s out of date. Both work, but session[] is preferred over
>@session.
>
>Dave

I took that as a request to update the wiki ;-)  (I''d received the 
same answer from Scott Barron a few weeks ago.)

-Rob

Hi James,

Thanks for the recommendation.  I haven''t bought it yet, but intend to.

Best regards,
Bill

----- Original Message -----
From: "James Ludlow" <jamesludlow@gmail.com>
To: <rails@lists.rubyonrails.org>
Sent: 2006-02-28 2:32 PM
Subject: Re: [Rails] Session magic question


On 2/28/06, Bill Walton <bill.walton@charter.net>
wrote:
> So Cart.new returns the object id which gets passed through the assignment
> operator to session[:cart].
>
> Maybe what''s throwing me it that the documentation on the Rails
wiki
> (http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions) shows
> assignments being done to what I thought was an instance variable:
>
> @session[:greeting] = "Hello world!"
>
> How come the Depot app doesn''t need to use @session[] instead of
session[]
> to store the Cart id?
>
> Maybe I''m confused on local vs. instance variables?

Based on your questions, and that you really seem to want to learn
this, I''d recommend Ruby for Rails.  It''s in beta right now,
but the
available PDF chapters already cover a lot of what you''re asking about
here.

http://www.manning.com/books/black
_______________________________________________
Rails mailing list
Rails@lists.rubyonrails.org
http://lists.rubyonrails.org/mailman/listinfo/rails

Hi Tom, and everyone who''s contributed to helping me get this!

It turns out I was wrong on all fronts...

I thought I was having a problem with the session hash because the record
wasn''t getting updated.  Turns out it wasn''t the session at
all.  The root
of the problem (which I obscured with a couple of others) turns out to be
that I wasn''t putting the data in the object using
''update_attributes''.  Duh
:-P

Thanks again for your help!

Bill


----- Original Message -----
From: "Tom Mornini" <tmornini@infomania.com>
To: <rails@lists.rubyonrails.org>
Sent: 2006-02-28 2:37 PM
Subject: Re: [Rails] Session magic question

> > On 2/28/06, Bill Walton <bill.walton@charter.net> wrote:
> >> So Cart.new returns the object id which gets passed through the
> >> assignment
> >> operator to session[:cart].
> >>
> >> Maybe what''s throwing me it that the documentation on the
Rails wiki
> >> (http://wiki.rubyonrails.com/rails/pages/HowtoWorkWithSessions)
shows
> >> assignments being done to what I thought was an instance variable:
> >>
> >> @session[:greeting] = "Hello world!"
> >>
> >> How come the Depot app doesn''t need to use @session[]
instead of
> >> session[]
> >> to store the Cart id?
> >>
> >> Maybe I''m confused on local vs. instance variables?
>
> No, you''re confused because there''s two ways to do it.
>
> And, it''s an instance variable (@session) -vs- a method call
(session
> []) in
> this case, I believe.
>
> --
> -- Tom Mornini
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

On Feb 28, 2006, at 1:04 PM, Bill Walton wrote:
> The root of the problem (which I obscured with a couple of others)
Isn''t learning wonderful? :-)

It''s not a job, it''s an adventure!

-- 
-- Tom Mornini