adamw

val insertUserInTx: IO[Int] = insertUser.transact(transactor)

// (2)  BEGIN; INSERT; COMMIT; sendEmail();
val result2: IO[Unit] = insertUserInTx.flatMap(_ => sendEmail)

// (3)  sendEmail(); BEGIN; INSERT; COMMIT;
val result3: IO[Int] = sendEmail.flatMap(_ => insertUserInTx)

adamw

// Re-useable effect descriptions
val sendEmail: IO[Unit] = IO(println("Sending email"))
val insertUser: ConnectionIO[Int] = 
  sql"INSERT INTO users(name, email) VALUES('Emily', 'emily@email.com')"
    .update.run

// (1)  BEGIN; INSERT; sendEmail(); COMMIT;
val insertThenSend: ConnectionIO[Unit] =
  insertUser.flatMap(_ => sendEmail.to[ConnectionIO])
  

adamw

val sendEmail: IO[Unit] = IO(println("Sending email"))
val sendEmailWithConnection: ConnectionIO[Unit] = 
  sendEmail.to[ConnectionIO]
val sendEmailInTx: IO[Unit] = sendEmailWithConnection.transact(transactor)

adamw

(1) BEGIN; INSERT; sendEmail(); COMMIT;
(2) BEGIN; INSERT; COMMIT; sendEmail();
(3) sendEmail(); BEGIN; INSERT; COMMIT;
(4) BEGIN; sendEmail(); INSERT; COMMIT;

adamw

def insertPerson(p: Person): ConnectionIO[Int] = 
  sql"INSERT INTO persons(name, age) VALUES(${p.name}, ${p.age})".update.run
def countPersons: ConnectionIO[Int] = 
  sql"SELECT COUNT(*) FROM persons".query[Int].unique

val insertAndCount = 
  insertPerson(Person("Pedro", 81)).flatMap(_ => countPersons)

adamw

val transactor: Transactor[IO] = ???
val result: IO[List[Person]] = personsQuery.transact(transactor)

val persons: List[Person] = result.unsafeRunSync()

adamw

// details on creating a transactor are omitted
val transactor: Transactor[IO] = ???
 
val result: IO[List[Person]] = personsQuery.transact(transactor)

adamw

import doobie._
import doobie.implicits._

case class Person(name: String, age: Int)
val personsQuery: ConnectionIO[List[Person]] = 
  sql"SELECT p.name, p.age FROM persons p".query[Person].to[List]

adamw

Functional Scala CRUD

We'll be adding a feature to Bootzooka, a skeleton Scala microservice/web application project.

This will involve using doobie, monix, tapir, http4s, circe and compile-time dependency injection.

If you'd like to follow along:

1. make sure you have Java & sbt installed. You can use sdkman for Java and popular package manages for sbt (e.g. brew)
2. git clone https://github.com/softwaremill/bootzooka.git

adamw

val TestConfig: Config = DefaultConfig
  .modify(_.email.emailSendInterval)
  .setTo(100.milliseconds)