.pure[Future] vs Future.successful in Scala

In Scala, .pure[Future] and Future.successful serve similar purposes, incase you are wondering which one to use go for anyone as there is not much of a difference but they are associated with different libraries and have some differences in their usage:

Cats Library (.pure[Future]):

  • .pure is a method provided by the Cats library, which is a popular library for functional programming in Scala.
  • It is not part of the standard Scala library.
  • Cats provides abstractions for working with different effect types, including Future.
  • .pure is used to lift a pure (non-effectful) value into a specified effect type, such as Future.
  • It is more aligned with functional programming concepts and type classes.
import cats.implicits._
import scala.concurrent.Future

val value: Int = 42
val futureValue: Future[Int] = value.pure[Future]

Standard Library (Future.successful):

  • Future.successful is part of the standard Scala library, and it’s used to create a successful (completed) Future with a specified value.
  • It’s simple and straightforward to use, as it doesn’t require any additional libraries or imports.
  • It’s commonly used for creating successful Future instances.
import scala.concurrent.Future

val value: Int = 42
val futureValue: Future[Int] = Future.successful(value)

In summary, if you’re using the Cats library or are working within a functional programming context, you might prefer .pure[Future] to lift values into a Future. However, if you’re looking for a simple and standard way to create a successful Future, you can use Future.successful. The choice between them depends on your project’s dependencies and your preferred style of programming.

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