Slick left outer join fetching whole joined row as option

Question

My join looks like this:

def byIdWithImage = for {
    userId <- Parameters[Long]
    (user, image) <- Users leftJoin RemoteImages on (_.imageId === _.id)          


        

Answer 1

Off the top of my head, I'd use a custom mapped projection. Something like this:

case class RemoteImage(id: Long, url: URL)

def byIdWithImage = for {
    userId <- Parameters[Long]
    (user, image) <- Users leftJoin RemoteImages on (_.imageId === _.id) if user.id === userId
} yield (user, maybeRemoteImage(image.id.? ~ image.url.?))

def maybeRemoteImage(p: Projection2[Option[Long], Option[URL]]) = p <> ( 
  for { id <- _: Option[Long]; url <- _: Option[URL] } yield RemoteImage(id, url),
  (_: Option[RemoteImage]) map (i => (Some(i id), Some(i url)))
)

Using scalaz (and its ApplicativeBuilder) should help reduce some of that boilerplate.