Mastering Kotlin

Creating a data class

To create a data class, we can add the data keyword to a class declaration as long as the class follows several specific rules:

• It is a primary constructor with at least one property
• It cannot be a sealed class, open, inner, or abstract

In this example, we define a data class, Article, which contains two primary constructor properties:

data class Article(val title: String, val author: String)

Primary constructor properties will be included in the generated implementations of copy(), equals(), hashCode(), and toString().

A data class may also contain properties that are not defined in the primary constructor:

data class Article(val title: String, val author: String) {    var snippet: String = ""}

Data class properties ...