Scala 3/API/scala/App

App

@nowarn("cat=deprecation&origin=scala\\.DelayedInit") trait App extends DelayedInit

The App trait can be used to quickly turn objects into executable programs. Here is an example:

object Main extends App { Console.println("Hello World: " + (args mkString ", ")) }

No explicit main method is needed. Instead, the whole class body becomes the “main method”.

args returns the current command line arguments as an array.

Caveats

It should be noted that this trait is implemented using the DelayedInit functionality, which means that fields of the object will not have been initialized before the main method has been executed.

Future versions of this trait will no longer extend DelayedInit.

Source
App.scala
class Object
trait Matchable
class Any

Value members

Concrete methods

final protected def args: Array[String]

The command line arguments passed to the application's main method.

Source
App.scala
final def main(args: Array[String]): Unit

The main method. This stores all arguments so that they can be retrieved with args and then executes all initialization code segments in the order in which they were passed to delayedInit.

Value Params
args

the arguments passed to the main method

Source
App.scala

Deprecated methods

@deprecated("the delayedInit mechanism will disappear", "2.11.0")
override def delayedInit(body: => Unit): Unit

The init hook. This saves all initialization code for execution within main. This method is normally never called directly from user code. Instead it is called as compiler-generated code for those classes and objects (but not traits) that inherit from the DelayedInit trait and that do not themselves define a delayedInit method.

Value Params
body

the initialization code to be stored for later execution

Deprecated
Definition Classes
Source
App.scala

Concrete fields

final val executionStart: Long

The time when the execution of this program started, in milliseconds since 1 January 1970 UTC.

Source
App.scala