Merge pull request #1719 from sgeorgakis/master

[SCALA-499] IOApp in Cats Effect

Author: dominiqueplante

cats-effects/src/main/scala/com/baeldung/scala/ioapp/ArgumentIOApp.scala

@@ -0,0 +1,15 @@
+package com.baeldung.scala.ioapp
+
+import cats.effect.{ExitCode, IO, IOApp}
+
+object ArgumentIOApp extends IOApp {
+
+  def run(args: List[String]): IO[ExitCode] = {
+    if (args.nonEmpty) {
+      IO.println(s"Running with args: ${args.mkString(",")}")
+        .as(ExitCode.Success)
+    } else {
+      IO.println("No args provided. Aborting").as(ExitCode(2))
+    }
+  }
+}

cats-effects/src/main/scala/com/baeldung/scala/ioapp/ContextIOApp.scala

@@ -0,0 +1,21 @@
+package com.baeldung.scala.ioapp
+
+import cats.effect._
+import cats.effect.unsafe.IORuntimeConfig
+
+import java.util.concurrent.Executors
+import scala.concurrent.ExecutionContext
+
+object ContextIOApp extends IOApp {
+
+  private val customExecutionContext: ExecutionContext =
+    ExecutionContext.fromExecutor(Executors.newWorkStealingPool(1))
+
+  override def run(args: List[String]): IO[ExitCode] = {
+    val computation = IO {
+      println(s"Running on thread: ${Thread.currentThread().getName}")
+    }
+
+    computation.evalOn(customExecutionContext).as(ExitCode.Success)
+  }
+}

cats-effects/src/main/scala/com/baeldung/scala/ioapp/ResourceIOApp.scala

@@ -0,0 +1,22 @@
+package com.baeldung.scala.ioapp
+
+import cats.effect.{ExitCode, IO, IOApp, Resource}
+
+import java.util.concurrent.Executors
+import scala.concurrent.ExecutionContext
+
+object ResourceIOApp extends IOApp {
+
+  val customExecutionContext: Resource[IO, ExecutionContext] =
+    Resource.make(
+      IO(ExecutionContext.fromExecutorService(Executors.newWorkStealingPool(1)))
+    ) { ec =>
+      IO.println("Shutting down execution contest").as(ec.shutdown())
+    }
+
+  def run(args: List[String]): IO[ExitCode] = customExecutionContext
+    .use { ec =>
+      IO.println(s"Running on thread: ${Thread.currentThread().getName}")
+    }
+    .as(ExitCode.Success)
+}

cats-effects/src/main/scala/com/baeldung/scala/ioapp/SimpleIOApp.scala

@@ -0,0 +1,9 @@
+package com.baeldung.scala.ioapp
+
+import cats.effect.{IO, IOApp}
+
+object SimpleIOApp extends IOApp.Simple {
+  val run: IO[Unit] = {
+    IO.println("Running with simple app")
+  }
+}