Have seen a few play apps' source and it feels like massive boilerplate and leaky promise/future/async crud everywhere.
Lets take this:
https://github.com/guardian/frontend/blob/master/article/app/controllers/ArticleController.scala
case class ArticlePage(article: Article, storyPackage: List[Trail], edition: String)
object ArticleController extends Controller with Logging {
def render(path: String) = Action { implicit request =>
val promiseOfArticle = Akka.future(lookup(path))
Async {
promiseOfArticle.map(_.map { renderArticle }.getOrElse { NotFound })
}
}
private def lookup(path: String)(implicit request: RequestHeader): Option[ArticlePage] = suppressApi404 {
// .. stuff omitted
}
private def renderArticle(model: ArticlePage)(implicit request: RequestHeader): Result = // .. omitted
}
Let's look at that render
method. What does it do? It's pretty hard to tell, even with a lot of the code removed. It's trying to render an article.
If we just wrote some vanilla code to do that, it would be:
def render(path:String) = {
renderArticle(lookup(path).getOrElse(NotFound))
}
So what's all that other stuff? We've got all the buzzwords covered:
- promise
- future
- async
Why is this here? Several of this apps controllers have this exact structure. Shouldn't this concern be separated somehow? Even the Action
DSL method
that starts this off sticks out like a sort thumb. This method is all unnecessary complexity. To figure out what it does, I have to know what futures
and promises are, and what Async
does, but moreover, almost none of this method's source is specific to the business logic being performed. Why?
Let's see some more boilerplate:
implicit request
- why do I have to type this in every controller? Shouldn't every controller have a request without me typing code?!views.html.article
- I really have to tell theArticleController
to use HTML and to use thearticle
view?Cached
- why is this in the controller? This should be a separate concern.
I realize that some of this might be because of Scala's type system, but it just feels like we've taken the same boilerplate from XML or Annotations and made it code and somehow that makes it OK.
I hated repeating myself and telling the framework what it should've already known in XML, XDoclet, and annotations. I don't like it any better in code.
I'd rather see more explicit patterns initially since Play was basically re-written from the ground up. Over time there seem to be some absorption occurring in the community and Typesafe/Play are answering.
One nice change which is being rolled out in 2.1 is the ability in a route to have a controller method defined on a class instead of an object only. Previously, with only objects, mocking resources used by controllers could be a real PITA.
As already mentioned the JSON API is being improved along with consolidation of the Promise/Future API's into one Future defined in the Scala 2.10 std libs.