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package code.lib.snippet
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future
import net.liftweb.util.CssSel
import net.liftweb.util.Helpers._
import scala.xml.{NodeSeq, Text}
import net.liftweb.http.js.JsCmd
import scala.util.{Failure, Success}
import net.liftweb.common.Logger
import net.liftweb.http.{S, SHtml}
import net.liftweb.http.js.JsCmds._
import code.comet.CommandComet
object AsyncRenderer extends Logger {
// The NodeSeq to use if the Future execution fails. If you want, you can allow the users to
// pass in custom NodeSeqs for such cases.
private val DefaultFailureContent = Text("Unfortunately, this operation could not be completed.")
/**
* This can be made made more configurable by adding more arguments. One additional
* argument could be the NodeSeq for the placeholder that's shown while the Future
* is not yet complete.
*
* @param renderer the Future with CssSel transforms that will be used for rendering
* your template when that Future completes.
* @param existingCometName name of a comet of type code.comet.CommandComet if such
* in instance has been already put on the page before. If not, no problem.
* @param template the original NodeSeq that was passed to your snippet instance and that
* will be transformed using the renderer that was passed to this method.
*/
def render(renderer: Future[CssSel],
template: NodeSeq,
existingCometName: Option[String] = None): NodeSeq = {
implicit val session = S.session.openOrThrowException("An active session is required")
val cometName = existingCometName getOrElse nextFuncName
var transforms: Option[CssSel] = None
val containerId = nextFuncName
// Currently LiftSession#buildDeferredFunction doesn't take arguments, so
// whatever we want to make available to the deferred function, we have to
// do it via closures, like we are doing with the 'transforms' var here.
val renderFn = session.buildDeferredFunction { () =>
val result = transforms match {
case Some(selector) => selector(template)
case None => DefaultFailureContent
}
val cmd = SetHtml(containerId, result)
CommandComet.sendJsCmd(cometName, cmd)
}
renderer.onComplete { result =>
result match {
case Failure(ex) =>
ex.printStackTrace()
error("An error occurred during async rendering", ex)
case Success(selector) =>
transforms = Some(selector)
}
renderFn()
}
renderer.map { sel =>
transforms = Some(sel)
}.recover { case ex: Throwable =>
ex.printStackTrace()
error("An error occurred while getting messages", ex)
}
// If an actor wasn't setup previously, add a new one just for our
// purposes.
val actor = existingCometName match {
case Some(_) => NodeSeq.Empty
case None => CommandComet.render(cometName)
}
// This is the content that will be displayed before the Future is completed.
// You can take an optional NodeSeq as an argument to this method if you want
// to allow the users to customize this template.
val placeholder =
<div id={containerId}>
<img alt="progress indicator" src="/assets/images/ajax-loader.gif" />
</div>
placeholder ++ actor
}
}
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