Packages

  • package root
    Definition Classes
    root
  • package cats

    The cats root package contains all the trait signatures of most Scala type classes.

    The cats root package contains all the trait signatures of most Scala type classes.

    Cats type classes are implemented using the approach from the Type classes as objects and implicits article.

    For each type class, cats provides three pieces: - Its signature: a trait that is polymorphic on a type parameter. Type class traits inherit from other type classes to indicate that any implementation of the lower type class (e.g. Applicative) can also serve as an instance for the higuer type class (e.g. Functor). - Type class 'instances, which are classes and objects that implement one or more type class signatures for some specific types. Type class instances for several data types from the Java or Scala standard libraries are declared in the subpackage cats.instances. - Syntax extensions, each of which provides the methods of the type class defines as extension methods (which in Scala 2 are encoded as implicit classes) for values of any type F; given that an instance of the type class for the receiver type (this) is in the implicit scope. Symtax extensions are declared in the cats.syntax package. - A set of laws, that are also generic on the type of the class, and are only defined on the operations of the type class. The purpose of these laws is to declare some algebraic relations (equations) between Scala expressions involving the operations of the type class, and test (but not verify) that implemented instances satisfy those equations. Laws are defined in the cats-laws package.

    Although most of cats type classes are declared in this package, some are declared in other packages: - type classes that operate on base types (kind *), and their implementations for standard library types, are contained in cats.kernel, which is a different SBT project. However, they are re-exported from this package. - type classes of kind F[_, _], such as cats.arrow.Profunctor" or cats.arrow.Arrow, which are relevant for Functional Reactive Programming or optics, are declared in the cats.arrow package. - Also, those type classes that abstract over (pure or impure) functional runtime effects are declared in the cats-effect library. - Some type classes for which no laws can be provided are left out of the main road, in a small and dirty alley. These are the alleycats.

    Definition Classes
    root
  • package data
    Definition Classes
    cats
  • AndThen
  • AppFunc
  • Binested
  • BinestedBifoldable
  • BinestedBitraverse
  • BinestedInstances
  • Chain
  • Cokleisli
  • Const
  • Cont
  • ContT
  • EitherK
  • EitherT
  • Func
  • IdT
  • IndexedReaderWriterStateT
  • IndexedState
  • IndexedStateT
  • Ior
  • IorT
  • Kleisli
  • KleisliFromFunctionPartiallyApplied
  • Nested
  • NonEmptyChainOps
  • NonEmptyList
  • NonEmptyMapOps
  • NonEmptySeq
  • NonEmptySetOps
  • NonEmptyVector
  • OneAnd
  • Op
  • OptionT
  • Reader
  • ReaderWriterState
  • ReaderWriterStateT
  • RepresentableStore
  • State
  • StateT
  • Store
  • Tuple2K
  • Validated
  • Writer
  • WriterT
  • ZipList
  • ZipSeq
  • ZipStream
  • ZipVector

final case class OptionT[F[_], A](value: F[Option[A]]) extends Product with Serializable

OptionT[F[_], A] is a light wrapper on an F[Option[A]] with some convenient methods for working with this nested structure.

It may also be said that OptionT is a monad transformer for Option.

For more information, see the documentation.

Linear Supertypes
Serializable, Serializable, Product, Equals, AnyRef, Any
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  1. OptionT
  2. Serializable
  3. Serializable
  4. Product
  5. Equals
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Instance Constructors

  1. new OptionT(value: F[Option[A]])

Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. def ===(that: OptionT[F, A])(implicit eq: Eq[F[Option[A]]]): Boolean
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def cata[B](default: ⇒ B, f: (A) ⇒ B)(implicit F: Functor[F]): F[B]

    Catamorphism on the Option.

    Catamorphism on the Option. This is identical to fold, but it only has one parameter list, which can result in better type inference in some contexts.

  7. def cataF[B](default: ⇒ F[B], f: (A) ⇒ F[B])(implicit F: FlatMap[F]): F[B]

    Effectful catamorphism on the Option.

    Effectful catamorphism on the Option. This is identical to foldF, but it only has one parameter list, which can result in better type inference in some contexts.

  8. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  9. def collect[B](f: PartialFunction[A, B])(implicit F: Functor[F]): OptionT[F, B]
  10. def compare(that: OptionT[F, A])(implicit o: Order[F[Option[A]]]): Int
  11. def contramap[B](f: (B) ⇒ A)(implicit F: Contravariant[F]): OptionT[F, B]
  12. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  13. def exists(f: (A) ⇒ Boolean)(implicit F: Functor[F]): F[Boolean]
  14. def filter(p: (A) ⇒ Boolean)(implicit F: Functor[F]): OptionT[F, A]
  15. def filterNot(p: (A) ⇒ Boolean)(implicit F: Functor[F]): OptionT[F, A]
  16. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  17. def flatMap[B](f: (A) ⇒ OptionT[F, B])(implicit F: Monad[F]): OptionT[F, B]
  18. def flatMapF[B](f: (A) ⇒ F[Option[B]])(implicit F: Monad[F]): OptionT[F, B]
  19. def flatTapNone[B](ifNone: ⇒ F[B])(implicit F: Monad[F]): OptionT[F, A]

    Perform an effect if the value inside the is a None, leaving the value untouched.

    Perform an effect if the value inside the is a None, leaving the value untouched. Equivalent to orElseF with an effect returning None as argument.

  20. def flatTransform[B](f: (Option[A]) ⇒ F[Option[B]])(implicit F: Monad[F]): OptionT[F, B]
  21. def fold[B](default: ⇒ B)(f: (A) ⇒ B)(implicit F: Functor[F]): F[B]
  22. def foldF[B](default: ⇒ F[B])(f: (A) ⇒ F[B])(implicit F: FlatMap[F]): F[B]

    Transform this OptionT[F, A] into a F[B].

    Transform this OptionT[F, A] into a F[B].

    Example:

    scala> import cats.implicits._
scala> import cats.data.OptionT

scala> val optionT: OptionT[List, Int] = OptionT[List, Int](List(Some(23), None))
scala> optionT.foldF(Nil)(v => List(v, v * 2))
res0: List[Int] = List(23, 46)
  23. def foldLeft[B](b: B)(f: (B, A) ⇒ B)(implicit F: Foldable[F]): B
  24. def foldRight[B](lb: Eval[B])(f: (A, Eval[B]) ⇒ Eval[B])(implicit F: Foldable[F]): Eval[B]
  25. def forall(f: (A) ⇒ Boolean)(implicit F: Functor[F]): F[Boolean]
  26. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  27. def getOrElse[B >: A](default: ⇒ B)(implicit F: Functor[F]): F[B]
  28. def getOrElseF[B >: A](default: ⇒ F[B])(implicit F: Monad[F]): F[B]
  29. def imap[B](f: (A) ⇒ B)(g: (B) ⇒ A)(implicit F: Invariant[F]): OptionT[F, B]
  30. def isDefined(implicit F: Functor[F]): F[Boolean]
  31. def isEmpty(implicit F: Functor[F]): F[Boolean]
  32. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  33. def map[B](f: (A) ⇒ B)(implicit F: Functor[F]): OptionT[F, B]
  34. def mapFilter[B](f: (A) ⇒ Option[B])(implicit F: Functor[F]): OptionT[F, B]
  35. def mapK[G[_]](f: ~>[F, G]): OptionT[G, A]

    Modify the context F using transformation f.

  36. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  37. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  38. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  39. def orElse(default: ⇒ OptionT[F, A])(implicit F: Monad[F]): OptionT[F, A]
  40. def orElseF(default: ⇒ F[Option[A]])(implicit F: Monad[F]): OptionT[F, A]
  41. def partialCompare(that: OptionT[F, A])(implicit p: PartialOrder[F[Option[A]]]): Double
  42. def semiflatMap[B](f: (A) ⇒ F[B])(implicit F: Monad[F]): OptionT[F, B]
  43. def semiflatTap[B](f: (A) ⇒ F[B])(implicit F: Monad[F]): OptionT[F, A]
  44. def show(implicit F: Show[F[Option[A]]]): String
  45. def subflatMap[B](f: (A) ⇒ Option[B])(implicit F: Functor[F]): OptionT[F, B]
  46. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  47. def toLeft[R](right: ⇒ R)(implicit F: Functor[F]): EitherT[F, A, R]
  48. def toLeftF[R](right: ⇒ F[R])(implicit F: Monad[F]): EitherT[F, A, R]
  49. def toNested: Nested[F, Option, A]

    Transform this OptionT[F, A] into a Nested[F, Option, A].

    Transform this OptionT[F, A] into a Nested[F, Option, A].

    An example where toNested can be used, is to get the Apply.ap function with the behavior from the composed Apply instances from F and Option, which is inconsistent with the behavior of the ap from Monad of OptionT.

    scala> import cats.implicits._
scala> import cats.data.OptionT
scala> val ff: OptionT[List, Int => String] =
     |   OptionT(List(Option(_.toString), None))
scala> val fa: OptionT[List, Int] = OptionT(List(Option(1), Option(2)))
scala> ff.ap(fa)
res0: OptionT[List,String] = OptionT(List(Some(1), Some(2), None))
scala> OptionT(ff.toNested.ap(fa.toNested).value)
res1: OptionT[List,String] = OptionT(List(Some(1), Some(2), None, None))
  50. def toRight[L](left: ⇒ L)(implicit F: Functor[F]): EitherT[F, L, A]
  51. def toRightF[L](left: ⇒ F[L])(implicit F: Monad[F]): EitherT[F, L, A]
  52. def transform[B](f: (Option[A]) ⇒ Option[B])(implicit F: Functor[F]): OptionT[F, B]
  53. def traverse[G[_], B](f: (A) ⇒ G[B])(implicit F: Traverse[F], G: Applicative[G]): G[OptionT[F, B]]
  54. val value: F[Option[A]]
  55. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  56. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  57. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  58. def withFilter(p: (A) ⇒ Boolean)(implicit F: Functor[F]): OptionT[F, A]

Inherited from Serializable

Inherited from Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

Ungrouped