scala - Slick and nesting case classes a no go? -


i using slick (and play framework) build application on top of existing database. cannot change database structure.

my database has following 2 tables:

meeting:

  • id (pk)
  • name
  • chairman_id (fk person.id)
  • houseman_id (fk person.id)

person:

  • id (pk)
  • first_name
  • last_name

i wanted define case classes this:

case class meeting (   id: int,   name: string,   chairman: person,   houseman: person )   case class person (    id: int,    firstname: string,    lastname: string )

but minimal slick documentation around this, looks have keep ids in case class rather using "person". correct?

whats best approach this? sorry relatively open question, new scala, slick , play.

thanks,

ed

you have foreign keys, don't translate case classes, translate ids:

case class meeting (   id: int,   name: string,   chairmanid: int,   housemanid: int)    case class person (   id: int,   firstname: string,   lastname: string)

and schema like:

 case class meeting (                    id: int,                    name: string,                    chairmanid: int,                    housemanid: int)   case class person (                   id: int,                   firstname: string,                   lastname: string)   class meetings(tag: tag) extends table[meeting](tag, "meeting") {   def * = (id, name, chairmanid, housemanid) <>(meeting.tupled, meeting.unapply)    def ? = (id.?, name, chairmanid, housemanid).shaped.<>({     r => import r._       _1.map(_ => meeting.tupled((_1.get, _2, _3, _4)))   }, (_: any) => throw new exception("inserting ? projection not supported."))    val id: column[int] = column[int]("id", o.autoinc, o.primarykey)   val name: column[string] = column[string]("name")   val chairmanid: column[int] = column[int]("chairmanid")   val housemanid: column[int] = column[int]("housemanid")    lazy val meetingchairmanfk =     foreignkey("meeting_chairman_fk", chairmanid, persons)(r => r.id, onupdate = foreignkeyaction.restrict, ondelete = foreignkeyaction.cascade)     lazy val meetinghousemanfk =     foreignkey("meeting_houseman_fk", housemanid, persons)(r => r.id, onupdate = foreignkeyaction.restrict, ondelete = foreignkeyaction.cascade)   }  lazy val meetings = new tablequery(tag => new meetings(tag))  class persons(tag: tag) extends table[person](tag, "person") {   def * = (id, firstname, lastname) <>(person.tupled, person.unapply)    def ? = (id.?, firstname, lastname).shaped.<>({     r => import r._       _1.map(_ => person.tupled((_1.get, _2, _3)))   }, (_: any) => throw new exception("inserting ? projection not supported."))    val id: column[int] = column[int]("id", o.autoinc, o.primarykey)   val firstname: column[string] = column[string]("firstname")   val lastname: column[string] = column[string]("lastname")   }  lazy val persons = new tablequery(tag => new persons(tag))

and used this:

val thismeeting = meetings.filter(_.name === "thismeeting").join(persons).on((m, p) => m.housemanid === p.id || m.chairmanid === p.id).list()

or using comprehension (which find more legible):

val thatmeething = (for {   m <- meetings   p <- persons if (p.id === m.chairmanid || p.id === m.housemanid) && m.name === "thatmeeting" } yield m.id).run

note second query corresponds implicit inner join, other types of join supported, can find them here.


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