Slick (play-slick) でクエリの共有 ref: http://qiita.com/koizuss@github/items/7e5cc8a566736b056e29

file0.scala

package repositories

import javax.inject.Inject

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future

import play.api.db.slick.{DatabaseConfigProvider, HasDatabaseConfigProvider}

import com.google.inject.ImplementedBy
import models.Tables
import models.Tables._
import slick.driver.JdbcProfile

@ImplementedBy(classOf[FooRepository])
trait FooRepositoryLike
  extends HasDatabaseConfigProvider[JdbcProfile] {

  def findById(id: String): Future[Option[(FooRow, BarRow)]]
}

class FooRepository @Inject()(protected val dbConfigProvider: DatabaseConfigProvider)
  extends FooRepositoryLike {
  import driver.api._

  def findById(id: String): Future[Option[(FooRow, BarRow)]] = {

    val query = for {
      f <- Foo if f.id === id.bind
      b <- Bar if b.id === f.barId
      // and more...
    } yield (f, b)

    db.run(query.result.headOption)
  }
}

file1.scala

class FooRepository @Inject()(protected val dbConfigProvider: DatabaseConfigProvider)
  extends FooRepositoryLike {
  import driver.api._

  /*
   * 切り出したクエリ
   */
  lazy val fooQuery = for {
    f <- Foo if f.id === id.bind
    b <- Bar if b.id === f.barId
    // and more...
  } yield (f, b)

  def findById(id: String): Future[Option[(FooRow, BarRow)]] = 
    db.run(fooQuery.filter(_._1.id === id.bind).result.headOption)

  def findAll(): Future[Seq[(FooRow, BarRow)]] = 
    db.run(fooQuery.sortBy(_._1.createAt.desc).result)
}

file2.scala

/*
 * 切り出したクエリ
 */
trait FooQuery
  extends HasDatabaseConfigProvider[JdbcProfile] {
  import driver.api._

  lazy val fooQuery = for {
    f <- Foo if f.id === id.bind
    b <- Bar if b.id === f.barId
    // and more...
  } yield (f, b)
}

class FooRepository @Inject()(protected val dbConfigProvider: DatabaseConfigProvider)
  extends FooRepositoryLike with FooQuery {
  import driver.api._

  def findById(id: String): Future[Option[(FooRow, BarRow)]] = 
    db.run(fooQuery.filter(_._1.id === id.bind).result.headOption)

  def findAll(): Future[Seq[(FooRow, BarRow)]] = 
    db.run(fooQuery.sortBy(_._1.createAt.desc).result)
}

// ----------------

class BazRepository @Inject()(protected val dbConfigProvider: DatabaseConfigProvider)
  extends BazRepositoryLike with FooQuery {
  import driver.api._

  def findById(id: String): Future[Option[(BazRow, FooRow, BarRow)]] = {
    val query = for {
      bz <- Baz if bz.id === id.bind
      (f, b) <- fooQuery if f.id === bz.fooId
    } yield (bz, f, b)

    db.run(query.result.headOption)
  }
}

file3.scala

trait FooQuery
  extends HasDatabaseConfigProvider[JdbcProfile] {
  import driver.api._

// ...