On Fri, Nov 20, 2009 at 8:17 AM, Alex Black <a...@alexblack.ca> wrote:
> Thanks Ross, that helps a lot.
>
> As a Lift newbie, I'm curious, would it be possible (in a future
> version of list) to re-use snippet instances for all calls during an
> HTTP request? Then people could share data between snippet methods
> (within a single snippet) by just writing regular member variables.
>
We made this change for Lift 1.1. So, if you're using 1.1, the same
instance of a snippet should be used for a given HTTP request.
>
> I'd imagine lift could even generate a requestVar representing each
> snippet for the developers, allowing snippets in a given HTTP request
> to access each other easily.
>
I don't think this is technically possible within the bounds of the type
system.
>
> On Nov 20, 11:09 am, Ross Mellgren <dri...@gmail.com> wrote:
> > RequestVar is the standard way of doing this. For example
> >
> > object MySharedInformation {
> > object myData extends RequestVar[List[Thing]](loadThings)
> > // ^^^^^^^^^^^ ^^^^^^^^^^
> > // Type of thing to store How to initialize
> > variable first time it's accessed
> >
> > private def loadThings: List[Thing] = ...
> >
> > }
> >
> > class Snippet1 {
> > import MySharedInformation.myData
> > def render(ns: NodeSeq): NodeSeq = {
> > myData.is.map(thing => { ... })
> > }
> >
> > }
> >
> > class Snippet2 {
> > import MySharedInformation.myData
> > ...
> >
> > }
> >
> > The lifetime of the value is during the current request processing and
> > any AJAX calls related to it.
> >
> > If you really want to initialize it in a snippet, then use a Box with
> > a RequestVar, like this:
> >
> > object MySharedInformation {
> > object myData extends RequestVar[Box[List[Thing]]](Empty)
> >
> > }
> >
> > class LoaderSnippet {
> > import MySharedInformation.myData
> > def render(ns: NodeSeq): NodeSeq = {
> > myData.set(Full(...))
> > }
> >
> > }
> >
> > class ReaderSnippet {
> > import MySharedInformation.myData
> > def render(ns: NodeSeq): NodeSeq = {
> > // If the data has not been loaded, default to an empty list
> > val data = myData.is.openOr(Nil)
> > ...
> > }
> >
> > }
> >
> > class OtherReaderSnippet {
> > import MySharedInformation.myData
> > def render(ns: NodeSeq): NodeSeq = {
> > // Do two entirely different things if the data has versus
> > has not been loaded
> > myData.is match {
> > case Full(data) => // do something when the data has been
> > loaded
> > case _ => // do something when the data has not been loaded
> > }
> > }
> >
> > }
> >
> > HTH,
> > -Ross
> >
> > On Nov 20, 2009, at 10:59 AM, Alex Black wrote:
> >
> > > I've got a template page, say foobar.html, that makes a number of
> > > calls to functions in a snippet, e.g. mysnippet.foo1, mysnippet.foo2,
> > > mysnippet.foo3.
> >
> > > I'd like to do some initial work in foo1, e.g. retrieve some data and
> > > do some work on it, then in foo2 and foo3 display parts of that data.
> >
> > > Whats the easiest way to do this? I think I misunderstood the lift
> > > book:
> >
> > > "That means that for each request, Lift creates a new instance of the
> > > snippet class to execute. Any changes you make to instance variables
> > > will be discarded after the request is processed."
> >
> > > I thought this meant that for a given HTTP request, there would be one
> > > (and only one) instance of my snippet, so I could call several of its
> > > methods and they could all access the snippet's member variables,
> > > which would then be discarded at the end of the request.
> >
> > > Am I going about this wrong? should I only have one snippet function
> > > per template?
> >
> > > Thx
> >
> > > - Alex
> >
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