Initialize an object in Kotlin

This article explores different ways to initialize an object in Kotlin.

1. Using Class Constructor

The standard way to initialize an object in Kotlin is with the class constructor. It can accept a set of parameters to initialize its fields, or it can be parameterless. Kotlin has a concise syntax for declaring properties and initializing them:

data class Person(var name: String? = null, var age: Int = 0)

fun main() {

val person = Person("John", 22)

println(person)

}

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2. Using Copy Constructor

The copy constructor is a special constructor for creating a new object from another object. It takes a single argument, which should be another instance of the same class. You can explicitly invoke another constructor within the copy constructor with the this() function.

data class Person(var name: String, var age: Int) {

// Copy Constructor

constructor(person: Person) : this(person.name, person.age)

}

fun main() {

val oldUser = Person("John", 22)

val newUser = Person(oldUser)

println(newUser)

}

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3. Properties

Another alternative is to get an instance of the class using the default constructor and set its properties later.

internal class Person() {

var name: String? = null

var age: Int = 0

override fun toString(): String {

return listOf(name, age).toString()

}

fun main() {

val person = Person()

person.name = "John"

person.age = 22

println(person)

}

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4. Using Anonymous Inner class

Although not recommended, you can use “Double Brace Initialization” to initialize the object. This creates an anonymous inner class with just an instance initializer in it.

internal open class Person(var name: String? = null, var age: Int = 0) {

override fun toString(): String {

return listOf(name, age).toString()

}

fun main() {

// Anonymous Class

val person = object : Person()

{

init {

// Initializer Block

name = "John"

age = 22

}

println(person)

}

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That’s all about initializing an object in Kotlin.

Initialize an object in Kotlin

1. Using Class Constructor

2. Using Copy Constructor

3. Properties

4. Using Anonymous Inner class

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