Nesting IO

IO example.scala

import cats.effect.IO
import scala.concurrent.{Await, Future}
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global

case class Repository()
case class MetaData(name: String)

trait APIClient {
  def getRepositories: IO[List[Repository]]

  def getMetadata(r: Repository): IO[MetaData]
}

def allMetaData(client: APIClient): IO[List[IO[MetaData]]] =
  client.getRepositories.map(
    _.map(
      repository =>
        client.getMetadata(repository)
    )
  )

// Naive implementation for demostration purposes
def printMetaDataOrderedByName(allMetaData: IO[List[IO[MetaData]]]): Unit =
  Await.result(
    Future.sequence(
      allMetaData.unsafeRunSync().map(_.unsafeToFuture())
    ),
    1.minute
  ).sortWith(_.name < _.name)
    .foreach(println)