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Asynchronous snippets in Lift 2.5

Asynchronous snippets in Lift 2.5

On my last post I wrote about using LAFutures on your snippets. And one of the things I said was that the syntax I was looking for was this:

val future1: LAFuture[String] = new LAFuture()

def render = {
  "#my-slow-loading-element *" #> future1

Well, over the last couple of nights I got to what I think is a great syntax:

class Sample extends Loggable {

  val f1: LAFuture[NodeSeq] = new LAFuture()
  val f2: LAFuture[NodeSeq] = new LAFuture()

  LAScheduler.execute( () => querySlowService1( f1 ) )
  LAScheduler.execute( () => querySlowService2( f2 ) )

  def render = {
    "#future1"                  #> f1 &
    ".diego"                    #> f2 &
    "data-name=another-future"  #> f2 &
    "#render-thread *"          #> Thread.currentThread().getName

Some details.

This post is about supporting LAFuture[NodeSeq], which basically says that the end user is responsible for fulfilling the Future with the data they want to see on the browser, and express it as a NodeSeq. This could be as simple as saying f1.satisfy(Text(Hello!)) or you could use more complex structures (like a complete html list)

You are also free to call your methods that will fulfill the LAFutures from anywhere you want. In this example, I call them as Lift materializes the snippet class, but you may as well call them after a form submit, or any other event.

One thing to remember is that the future in your css selector will replace the element you selected, so you cannot specify something like "#future1 *", you have to use "#future1". If you provide an element with an ID attribute, that’s great and we use that internally to then lookup the item, once the Future has a value. If not, we go ahead and add an ID attribute to your element. This is what you see when we select ".diego" and "data-name=another-future"

But other than that, your application just deals with LAFutures and Lift does the rest (well, this code is not part of Lift yet, but I’m hoping we can add it to the 3.0 branch.)

Sample application and code.

You can find a fully runnable application that includes the code listed here on github (on the la-futures-2 branch).

Thank you for reading and don’t hesitate to leave a comment/question.



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