Using guice when creating a custom Action using ActionBuilder in play - scala

Question

How can I use guice when creating a custom Action using ActionBuilder?
It seems to complain with "not found: value MyAction" if I change the ActionBuilder from a object to a class.
I have this but it doesn't work:
case class MyModel(name: String, request: Request[A]) extends WrappedRequest[A](request)
class MyAction #Inject()(userService: UserService) extends ActionBuilder[MyModel] {
def invokeBlock[A](request: Request[A], block: (MyModel[A]) => Future[SimpleResult]) = {
val abc = loadAbc(request)
block(new MyModel(abc, request))
}
def loadAbc(rh: RequestHeader): String {
"abc" // just for testing
}
}
So changing it from an object to a class causes it to fail, and I tried keeping it as an object but then it doesn't compile correctly.
How can I get this to work?
I have it working just fine in my controllers.

Answer 1

With a few minor corrections, what you've got seems to work already. All you've got to do is inject the guice-instantiated instance of MyAction into your controller, and then you can use the instance (rather than trying to use the MyAction class name).
This works with Play 2.3:
import scala.concurrent.Future
import javax.inject.{Inject, Singleton}
import play.api.mvc._
class UserService() {
def loadAbc(rh: RequestHeader) = "abc"
}
class MyModel[A](val name: String, request: Request[A]) extends WrappedRequest[A](request)
class MyAction #Inject()(userService: UserService) extends ActionBuilder[MyModel] {
def invokeBlock[A](request: Request[A], block: (MyModel[A]) => Future[Result]) = {
val abc = userService.loadAbc(request)
block(new MyModel(abc, request))
}
}
#Singleton
class Application #Inject() (myAction: MyAction) extends Controller {
def index = myAction { request =>
Ok(request.name)
}
}
You can't use object because that violates the design of Guice. object is a singleton instantiated by Scala itself and cannot have instance variables, whereas Guice needs to be able to instantiate classes on the fly so that it can inject dependencies.

Answer 2

I think your code should work if you use it like this:
class MyClass #Inject()(myAction: MyAction) {
val echo = myAction { request =>
Ok("Got request [" + request + "]")
}
}