Session vars are stored in memory (only) and are meant for short-term
persistent variable storage. You have to CFLOCK them, although there
have been some changes to this with the advent of CFMX. Your typical
default session var expires after 20 minutes of inactivity. However,
assuming the max expiration time has been extended in the CF
Administrator, you can expire them after a longer period of time.
Session vars do not scale across a server cluster since they are held in
a particular server's memory. Session vars are structures, so you have
the ability to natively store complex values within them, like arrays.
Client variables were intended for longer-term persistent value
storage... Expiration times measured in days; not minutes. They are
stored either in the Windows registry (or a facsimile thereof on *nix
systems), an external database or in cookies. Since they are not stored
in memory you do not need to CFLOCK them. Client variables are meant to
hold simple values, and do not natively support the storage of complex
values like arrays. Since a client var can be stored in a db (or I
suppose in a cookie) it can be used for persistent storage in a
clustered server environment.
Client vars can be extended so they expire just like session vars. Put
something like this in an application.cfm:
<cfset
variables.VisitChk=DateCompare(DateAdd('n',(20*-1),CreateODBCDateTime(NO
W())),client.LastVisit)>
<cfif Compare(variables.VisitChk,"-1")>
.. Uh oh. 20 minutes of inactivity have passed.
Delete the user's cvars...
</cfif>
Using WDDX you can even use them to store complex structures if needed.
That tutorial I mentioned in another thread (at http://halhelms.com)
will spell all that out, and explain the expiration thingie I copied,
above.
What did I miss?
--Matt Robertson--
MSB Designs, Inc.
http://mysecretbase.com
-----Original Message-----
From: Ben Doom [mailto:bdoom@;moonbow.com]
Sent: Thursday, October 31, 2002 8:15 PM
To: CF-Talk
Subject: client vs. session
I read up a bit on client and session scopes, and am a bit confused.
Can someone explain to me the difference between them? All I can really
find is that I have a bit more control over where, for example, session
variables are stored.
Feeling unscoped....
--Ben Doom
Programmer & General Lackey
Moonbow Software
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
Archives: http://www.houseoffusion.com/cf_lists/index.cfm?forumid=4
Subscription: http://www.houseoffusion.com/index.cfm?sidebar=lists&body=lists/cf_talk
FAQ: http://www.thenetprofits.co.uk/coldfusion/faq
Signup for the Fusion Authority news alert and keep up with the latest news in
ColdFusion and related topics. http://www.fusionauthority.com/signup.cfm
