Hands-On Object-Oriented Programming with Kotlin

Companion functions and interfaces

Interfaces can be implemented by companion objects as well as by normal and object classes. Let's take a look at how this can be done:

1. Create an Employee class with two properties, name and id, and an interface, EmployeeInterface, with add in the function signature:

data class Employee(val name: String, val id: Int)interface EmployeeInterface{    fun create(name: String, id: Int) : Employee}class EmployeeFactory {    companion object : EmployeeInterface{         override fun add(name:String, id: Int): Employee {            return Employee(name,id)        }    }}

This function takes two variables and returns the Employee object.

2. Create a class, EmployeeFactory, and implement the interface in the companion object. Provide the implementation ...