Removendo código duplicado com funções.

CityController.scala

package controllers.nereida

import play.api._
import play.api.mvc._
import play.api.data._
import play.api.data.Forms._
import play.api.libs.json.{Json, JsValue}
import models.nereida.City
import persistence.Prevayler
import persistence.commands.city.{AddNewCity, DeleteCity, UpdateCity, FindAllCities, FindCityById}
import views._

object CityController extends Controller {
  
  val cityMapping = ( "name" -> nonEmptyText )

  val cityForm = Form(
    mapping("name" -> nonEmptyText, "id" -> nonEmptyText)(City.apply)(City.unapply)
  )
  
  def index = Action { implicit request =>
    val cities = Prevayler.system.executeQuery( FindAllCities() )
    Created( Json.toJson(cities) )
  }

  def build = Action {
    Ok(views.html.nereida.city.cityForm(cityForm));
  }

  def create = processJSONRequest { 
    implicit json => {
      val city = Prevayler.system.executeTransaction( AddNewCity(json) )
      Created(Json.toJson(city))
    }
  }
  
  def show(id:String) = processQuery {
    Prevayler.system.executeQuery( FindCityById(id) )
  }

  def edit(id:String) = processQuery { 
    Prevayler.system.executeQuery( FindCityById(id) ) 
  }

  def update(id:String) = processJSONRequest { 
    implicit json => {
      val city = Prevayler.system.executeTransaction( UpdateCity(id, json) )
      Created(Json.toJson(city))
    }
  }

  def destroy(id:String) = Action { implicit request =>
    val city = Prevayler.system.executeTransaction( DeleteCity(id) )
    Ok(Json.toJson(city))
  }

  //aux functions
  def processJSONRequest(innerFunction: JsValue => Result) = {
    Action { 
      implicit request => {
        Form(cityMapping).bindFromRequest.fold(
          errors => BadRequest(errors.errorsAsJson),
          value => {
            request.body.asJson.map { json => 
              innerFunction(json)
            }.getOrElse {
              BadRequest(Json.toJson(Map("error" -> "invalid json")))
            }
          }
        )
      }
    }
  }

  def processQuery(innerFunction:  => Option[City]) = {
    Action {
      innerFunction.map { city => 
        Ok(views.html.nereida.city.cityForm(cityForm.fill( city )))
      }.getOrElse {
        BadRequest(Json.toJson(Map("error" -> "invalid json")))
      }
    }
  }
}