Slick select row by id - scala

Question

Selecting a single row by id should be a simple thing to do, yet I'm having a bit of trouble figuring out how to map this to my object.
I found this question which is looking for the same thing but the answer given does not work for me.
Currently I have this that is working, but it doesn't seem as elegant as it should be.
def getSingle(id: Long):Option[Category] = withSession{implicit session =>
(for{cat <- Category if cat.id === id} yield cat ).list.headOption
//remove the .list.headOption and the function will return a WrappingQuery
}
I feel getting a list then taking headOption is just bulky and unnecessary. I must be missing something.
If it helps, here is more of my Category code
case class Category(
id: Long = 0L,
name: String
)
object Category extends Table[Category]("categories"){
def name = column[String]("name", O.NotNull)
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def * = id ~ name <> (Category.apply _, Category.unapply _)
...
}
Is there an easier way to just get an Option[T] from an ID using Slick?
Solution There was a driver issue. I couldn't use .firstOption but upgraded to mysql jdbc 5.1.25 and all is well!

Answer 1

You can do this:
def getSingle(id: Long):Option[Category] = withSession{implicit session =>
Query(Category).where(_.id === id).firstOption
}
If you use this query quite often then you should consider QueryTemplate:
val byId = t.createFinderBy( t => t.id )
This will create a precompiled prepared statement that you can use from your method
def getSingle(id: Long):Option[Category] = byId(id).firstOption

Answer 2

Firstly, you may try is to use desugared version of the same code:
Category.filter{ _.id === id }.list.headOption
It looks much cleaner.
Also you may use firstOption method:
Category.filter{ _.id === id }.firstOption

Answer 3

I am using slick 1.0.1 with Play 2.2.1 and the following works for me.
val byId = createFinderBy(_.id)
Then call it from a method.
def findById(id: Int): Option[Category] = DB.withSession { implicit session =>
Category.byId(id).firstOption
}
Please note, the DB.withSession is a method from the play framework.
If you are not using Play, the method would be something like below.
def findById(id: Int)(implicit session: Session): Option[Category] = {
Category.byId(id).firstOption
}