Companion objects in Scala

Question

Please explain what is the companion object. I'd appreciate if you shared an example too

Answer 1

When a singleton object is named the same as a class, it is called a companion object. A companion object must be defined inside the same source file as the class. Here is an example:

class Main {

    def sayHelloWorld() {

        println("Hello World");

    }

}

object Main {

    def sayHi() {

        println("Hi!");

    }

}

In this class, you can both: instantiate Main and call sayHelloWorld() or call the sayHi() method on the companion object directly, like this:

var aMain : Main = new Main();

aMain.sayHelloWorld();

Main.sayHi();