Packages

t

cats.effect

IOApp

trait IOApp extends AnyRef

App type that runs a cats.effect.IO. Shutdown occurs after the IO completes, as follows:

- If completed with ExitCode.Success, the main method exits and shutdown is handled by the platform.

- If completed with any other ExitCode, sys.exit is called with the specified code.

- If the IO raises an error, the stack trace is printed to standard error and sys.exit(1) is called.

When a shutdown is requested via a signal, the IO is canceled and we wait for the IO to release any resources. The process exits with the numeric value of the signal plus 128.

import cats.effect._
import cats.implicits._

object MyApp extends IOApp {
  def run(args: List[String]): IO[ExitCode] =
    args.headOption match {
      case Some(name) =>
        IO(println(s"Hello, ${name}.")).as(ExitCode.Success)
      case None =>
        IO(System.err.println("Usage: MyApp name")).as(ExitCode(2))
    }
}
Source
IOApp.scala
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Abstract Value Members

  1. abstract def run(args: List[String]): IO[ExitCode]

    Produces the IO to be run as an app.

    Produces the IO to be run as an app.

    returns

    the cats.effect.ExitCode the JVM exits with

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
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  2. final def ##(): Int
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  8. def finalize(): Unit
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  9. final def getClass(): Class[_]
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  10. def hashCode(): Int
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  11. final def isInstanceOf[T0]: Boolean
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  12. final def main(args: Array[String]): Unit

    The main method that runs the IO returned by run and exits the JVM with the resulting code on completion.

  13. final def ne(arg0: AnyRef): Boolean
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  14. final def notify(): Unit
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  15. final def notifyAll(): Unit
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  16. final def synchronized[T0](arg0: ⇒ T0): T0
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  17. implicit def timer: Timer[IO]

    Provides an implicit timer instance for the app.

    Provides an implicit timer instance for the app.

    On the JVM, the default lazily constructed from the global execution context. Override to avoid instantiating this execution context.

    On scala.js, the default is Timer.global.

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  18. def toString(): String
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  19. final def wait(): Unit
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  20. final def wait(arg0: Long, arg1: Int): Unit
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  21. final def wait(arg0: Long): Unit
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