zio-slick-interop
Small library, that provides interop between Slick and ZIO
How to use
Include zio-slick-interop in your build:
libraryDependencies += "io.scalac" %% "zio-slick-interop" % "0.3.0"
It gives you a couple of nice things:
1. DatabaseProvider service
Database is usually a dependency for your other services. Since ZLayer is the best and recommended way to do DI with ZIO,
zio-slick-interop provides some convenience bindings for using slick with ZLayer.
Specifically, it's slick.interop.zio.DatabaseProvider, which is a service, defined by ZLayer guidelines and provides access to underlying slick database.
You'd generally want to use it when defining your repository services, like the following.
Say we have a simple raw Slick table:
// import your specific DB driver here
import slick.jdbc.H2Profile.api._
final case class Item(id: Long, name: String)
// Raw Slick table
object ItemsTable {
class Items(tag: Tag) extends Table[Item](tag, "items") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def name = column[String]("name")
def * = (id, name) <> ((Item.apply _).tupled, Item.unapply _)
}
val table = TableQuery[ItemsTable.Items]
}And we want to have a repository service on top of it with the following contract:
import zio._
trait ItemRepository {
def getById(id: Long): IO[Throwable, Option[Item]]
}Then we can implement it as a database-agnostic Slick repository using DatabaseProvider:
import zio._
import slick.interop.zio.DatabaseProvider
// adds ZIO.fromDBIO extension
import slick.interop.zio.syntax._
object SlickItemRepository {
val live: ZLayer[Has[DatabaseProvider], Throwable, Has[ItemRepository]] =
ZLayer.fromServiceM { db =>
db.profile.map { profile =>
import profile.api._
new ItemRepository {
private val items = ItemsTable.table
def getById(id: Long): IO[Throwable, Option[Item]] = {
val query = items.filter(_.id === id).result
ZIO.fromDBIO(query).map(_.headOption).provide(Has(db))
}
}
}
}
}SlickItemRepository.live is a repository layer that depends on raw underlying database.
You can notice ZIO.fromDBIO which is provided by zio-slick-interop and is described below.
2. Lifting DBIO into ZIO
There's a syntax extension allowing to lift DBIO actions into ZIO:
import slick.interop.zio.syntax._
import slick.interop.zio.DatabaseProvider
import zio._
// import your specific DB driver here
import slick.jdbc.H2Profile.api._
val insert = ItemsTable.table += Item(0L, "name")
val z: ZIO[Has[DatabaseProvider], Throwable, Int] = ZIO.fromDBIO(insert)This is a ZIO, that can be run given a DatabaseProvider is present in the environment.
slick.interop.zio.syntax._ imported.
There's also ZIO.fromStreamingDBIO, which works with streaming slick actions.
When executing a sequence of actions (when "flatMap-ing"), in the context of a transaction with transactionally for example,
Slick requires an implicit ExecutionContext in scope. For this use-case, another overload to ZIO.fromDBIO takes a function with an
ExecutionContext as argument:
import slick.interop.zio.syntax._
import slick.interop.zio.DatabaseProvider
import zio._
// import your specific DB driver here
import slick.jdbc.H2Profile.api._
import scala.concurrent.ExecutionContext
val id: Long = ???
val z: ZIO[Has[DatabaseProvider], Throwable, Unit] =
ZIO.fromDBIO { implicit ec: ExecutionContext =>
(for {
_ <- ItemsTable.table += Item(0L, "name")
_ <- ItemsTable.table.filter(_.id === id).map(_.name).update("new name")
} yield ()).transactionally
}Creating a DatabaseProvider.
DatabaseProvider provides a live layer that needs:
- a typesafe
Config, that points to a standard Slick configuration block; - specific database backend you're using.
Here's an example of creating a DatabaseProvider layer:
import zio._
import com.typesafe.config.Config
import slick.interop.zio.DatabaseProvider
val rootConfig: Config = ???
val dbConfigLayer = ZLayer.fromEffect (ZIO.effect(rootConfig.getConfig("db")))
val dbBackendLayer = ZLayer.succeed(slick.jdbc.H2Profile)
(dbConfigLayer ++ dbBackendLayer) >>> DatabaseProvider.liveDeveloped by Scalac