Thanks for the tips...it was educational! - Kinley
>From: "gyrus" <[EMAIL PROTECTED]> >Reply-To: [EMAIL PROTECTED] >To: CF-Talk <[EMAIL PROTECTED]> >Subject: Re: Request Scope Questions >Date: Sun, 11 Nov 2001 03:59:32 -0000 > > > I've been trying to brush up on my CF skills and I'm a bit confused with > > Request Variables. > >The request scope lasts for the duration of each request. If >you define request.var, every file (includes, custom tags, >whatever) that's processed from then on in the course of >that HTTP request has access to request.var. > >Session variables persist for as long as the session timeout >(set in CF Admin or <cfapplication> tag), and are specific to each >client. Application variables' persistence are again controlled >by CF Admin or <cfapplication> settings, and are specific to each >application (as defined with the <cfapplication> tag). > >Both session and application variables (and server variables) >need to be locked when read or written to. Check out > >ColdFusion Locking Best Practices >http://www.allaire.com/Handlers/index.cfm?ID=17318 > >Locking in ColdFusion >http://www.allaire.com/handlers/index.cfm?ID=17196 > >To Lock or Not To Lock >http://www.defusion.com/articles/index.cfm?ArticleID=105 > >for different views of locking. I found these articles kind of confusing >when taken together, each has a different angle. But you should >gain something between them. I don't understand the technicalities of >locking, but as I understand it the risk of clashes in CF accessing >application/session/server variables is due to how they are stored >in memory. There's the risk of memory leaks if there's a clash here. >The request scope is treated differently and doesn't carry that >risk (wow, listen to the tech jargon! ;) and hence you don't need >to put a lock around each time a request variable is written to or >read from. > >Request variables are often talked of just in the context of custom >tags, cos the fact that they can be accessed from anywhere >during one request means they're useful for custom tags to >talk to each other. But I use them quite a bit. I set all stuff >like DSN names and passwords in application.cfm using the >request scope. Also, any session variables that are needed >frequently, I transfer them to the request scope in application.cfm. >That way, I put one lock around this chunk of 'transfer' code, >and don't need to lock every time a session variable is needed. > >A couple of notes here: if you do this, use something like > ><cfset request.var=Duplicate(session.var)> > >to transfer the variable. If you don't use Duplicate() - correct >me if I'm wrong someone! - then request.var just becomes a >'pointer' to session.var, and session.var is still actually read when >you refer later to request.var (rendering the whole business kind >of redundant!). Duplicate() - which is only available in CF4.5+ - >makes request.var a 'deep' copy of session.var, and then >request.var technically has nothing to do with session.var >except having the same value. > >Also, I think the 'scope' attribute of <cflock> is new in 4.5 (one >of those articles above explains how to use it). Use it! > >I think there was a recent thread about how this kind of practice >affects processing speed. I haven't yet done any really high-traffic >sites where this might be a concern, so the convenience of the >request scope is great, for now. > >hth, > >- Gyrus > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Get the mailserver that powers this list at http://www.coolfusion.com FAQ: http://www.thenetprofits.co.uk/coldfusion/faq Archives: http://www.mail-archive.com/[email protected]/ Unsubscribe: http://www.houseoffusion.com/index.cfm?sidebar=lists
