# Covariant Nothing Object

DevFeed: [Covariant Nothing Object](<https://devfeed.tech/articles/covariant-nothing-object-39199.md>)

Original publisher: [Read original article](<https://kt.academy/article/ak-covariant-nothing-object>)

Published: 2023-02-13T00:15:00Z

Content type: tutorial

Language: en

Sources: [Kt. Academy](<https://devfeed.tech/sources/kt-academy.md>)

Topics: [Kotlin](<https://devfeed.tech/topics/kotlin.md>), [sealed class](<https://devfeed.tech/topics/sealed-class.md>), [Data structures](<https://devfeed.tech/topics/data-structures.md>), [Library](<https://devfeed.tech/topics/library.md>)

Tags: [data-structure](<https://devfeed.tech/tags/data-structure.md>), [kotlin](<https://devfeed.tech/tags/kotlin.md>), [object](<https://devfeed.tech/tags/object.md>), [sealed-class](<https://devfeed.tech/tags/sealed-class.md>), [standard-library](<https://devfeed.tech/tags/standard-library.md>), [type-parameter](<https://devfeed.tech/tags/type-parameter.md>), [workshop-learning-programming](<https://devfeed.tech/tags/workshop-learning-programming.md>)

## AI overview

This Kotlin developer article describes the "Covariant Nothing Object" pattern: using a covariant generic type with Nothing so a singleton object can represent an empty value across compatible types. It relates the pattern to immutable linked lists, Kotlin's standard library, generic messages, and scheduled tasks.

## Source excerpt

The pattern we are all using, but no-one talks about it.