Up and Running with the Typelevel Stack

Up and Running with the Typelevel Stack

• 1.
  Up and Runningwith the Typelevel Stack Scala Italy 2018
• 2.
  Cats & Cats-Effect ●Lightweight functional programming library ● Provides abstractions that help with pure FP ● Aims to make code highly composable and reusable ● One of the most important concept is “Programs as values”
• 3.
  Pure Functional Programming ●Code completely free of side-effects ● Effects are modelled as values to be executed by the runtime ● The IO data type is an example of such an effect type ● We can model our entire application as a single value of IO
• 4.
  Http4s ● Lightweight typeful,pure functional http library ● Makes it very easy to build classic server applications ● Purely functional, but also very performant ● Offers a DSL for easily matching HTTP routes
• 5.
  type Service =Request => IO[Response]
• 6.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) }
• 7.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) } Request
• 8.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) } IO[Response]
• 9.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) } Method
• 10.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) } Path
• 11.
  Http4s DSL -example HttpService[IO] { case GET -> Root / name => Ok(s“Hello $name”) } String
• 12.
  Circe ● Lightweight JSONlibrary ● Built upon Cats and Shapeless ● Allows us to derive encoders and decoders for our custom data types ● One of the most widely used JSON libraries in Scala
• 13.
  Doobie ● Functional abstractionover JDBC ● Allows us to represent database programs as values of the ConnectionIO data type ● We can then turn values of ConnectionIO into values of IO as a transaction. ● Automatic mapping of query results to case classes
• 14.
  Doobie - example valallUsers: ConnectionIO[List[User]] = sql"SELECT * FROM user".query[User].to[List] val luka: ConnectionIO[Option[User]] = sql"SELECT * FROM user WHERE $name = ‘Luka’" .query[User].option val program: IO[List[User]] = allUsers.transact(xa)
• 15.
  Let’s start! Clone theworkshop repo: https://github.com/LukaJCB/scala-italy-workshop Documentation and assignments are in the README.md