CODEWITHSUNDEEP
scalagenericsslickslick-3.0
Ferdy
Ferdy

Reputation: 507

Slick table does not take type parameter

I'm playing around with slick 3.0.0's new DBIO api but am having some problem with generics.

With this code:

import scala.concurrent._

import slick.driver.MySQLDriver.api._
import slick.lifted.AbstractTable

object Crud {

  def fetchById[T: AbstractTable[R], R](db: Database, table: TableQuery[T], id: Int, rowId: T => Rep[Int]): Future[Option[T]] = {
    val fetchByIdQuery: Query[T, R, Seq] = table.filter(row => rowId(row) === id)

    db.run(fetchByIdQuery.result)
  }
}

The compiler says that AbstractTable does not take any Type parameters. I don't understand this with a declaration as seen here https://github.com/slick/slick/blob/3.0/slick/src/main/scala/slick/lifted/AbstractTable.scala.

slick.lifted.AbstractTable[R] does not take type parameters
def fetchById[T: AbstractTable[R], R](db: Database, table: TableQuery[T], id: Int, rowId: T => Rep[Int]): Future[Option[T]] = {

I suspect this is also the cause of this error.

type mismatch;
 found   : slick.lifted.Query[T,T#TableElementType,Seq]
 required: slick.driver.MySQLDriver.api.Query[T,R,Seq]
    (which expands to)  slick.lifted.Query[T,R,Seq]
    val fetchByIdQuery: Query[T, R, Seq] = table.filter(row => rowId(row) === id)

Any advice?

Upvotes: 4

Views: 1215

Answers (1)

Bhavya Latha Bandaru
Bhavya Latha Bandaru

Reputation: 1108

Try it this way 

T <: AbstractTable[R]  // instead of T : AbstractTable[R]

so it should look like below

Object Crud {
def fetchById[T <: AbstractTable[R], R](db: Database, table: TableQuery[T], id: Int, rowId: T => Rep[Int])
 : Future[Option[T#TableElementType]] =  {
  val fetchByIdQuery = table.filter(row => rowId(row) === id)
  db.run(fetchByIdQuery.result.headOption)
 }
}

Upvotes: 1

Related Questions