Hello everyone, Someone can tell me wich is the best way to create a singleton, I had read something about "by lazy" but also another property like by DelegatesExt.notNullSingleValue()

Also could use

companion object

... "The companion object is a singleton, and its members can be accessed directly via the name of the containing class" https://kotlinlang.org/docs/tutorials/kotlin-for-py/objects-and-companion-objects.html

Thanks a lot, but what happen when I do an instance of the Singleton object, Need I use the property "by Lazy" or "by DelegatesExt.notNullSingleValue()" in my object?

If you use

object Singleton

, you just refer to

Singleton

. So, for example, if you had:

object Singleton {
  fun doSomethingTrulyAwesome() {
    TODO()
  }
}

...then elsewhere you could just call

SIngleton.doSomethingTrulyAwesome()

. However, manual singletons (such as

object

) are not very flexible, particularly when it comes to testing. You might want to look into "dependency inversion" options, such as Koin or Kodein, at some point.

If you start using singletons a lot, as Mark Murphy said, consider a dependency injection framework such as Spring, which by the way has first class support from creating singletons via annotations, or programmatically. See https://spring.io/blog/2017/08/01/spring-framework-5-kotlin-apis-the-functional-way