object Future
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- final def apply[T](body: => T)(implicit executor: ExecutionContext): Future[T]
Starts an asynchronous computation and returns a
Future
instance with the result of that computation.Starts an asynchronous computation and returns a
Future
instance with the result of that computation.The following expressions are equivalent:
val f1 = Future(expr) val f2 = Future.unit.map(_ => expr) val f3 = Future.unit.transform(_ => Success(expr))
The result becomes available once the asynchronous computation is completed.
- T
the type of the result
- body
the asynchronous computation
- executor
the execution context on which the future is run
- returns
the
Future
holding the result of the computation
- final def delegate[T](body: => Future[T])(implicit executor: ExecutionContext): Future[T]
Starts an asynchronous computation and returns a
Future
instance with the result of that computation once it completes.Starts an asynchronous computation and returns a
Future
instance with the result of that computation once it completes.The following expressions are semantically equivalent:
val f1 = Future(expr).flatten val f2 = Future.delegate(expr) val f3 = Future.unit.flatMap(_ => expr)
The result becomes available once the resulting Future of the asynchronous computation is completed.
- T
the type of the result
- body
the asynchronous computation, returning a Future
- executor
the execution context on which the
body
is evaluated in- returns
the
Future
holding the result of the computation
- final def failed[T](exception: Throwable): Future[T]
Creates an already completed Future with the specified exception.
Creates an already completed Future with the specified exception.
- T
the type of the value in the future
- exception
the non-null instance of
Throwable
- returns
the newly created
Future
instance
- final def find[T](futures: collection.immutable.Iterable[Future[T]])(p: (T) => Boolean)(implicit executor: ExecutionContext): Future[Option[T]]
Asynchronously and non-blockingly returns a
Future
that will hold the optional result of the firstFuture
with a result that matches the predicate, failedFuture
s will be ignored.Asynchronously and non-blockingly returns a
Future
that will hold the optional result of the firstFuture
with a result that matches the predicate, failedFuture
s will be ignored.- T
the type of the value in the future
- futures
the
scala.collection.immutable.Iterable
of Futures to search- p
the predicate which indicates if it's a match
- returns
the
Future
holding the optional result of the search
- final def firstCompletedOf[T](futures: IterableOnce[Future[T]])(implicit executor: ExecutionContext): Future[T]
Asynchronously and non-blockingly returns a new
Future
to the result of the first future in the list that is completed.Asynchronously and non-blockingly returns a new
Future
to the result of the first future in the list that is completed. This means no matter if it is completed as a success or as a failure.- T
the type of the value in the future
- futures
the
IterableOnce
of Futures in which to find the first completed- returns
the
Future
holding the result of the future that is first to be completed
- final def foldLeft[T, R](futures: collection.immutable.Iterable[Future[T]])(zero: R)(op: (R, T) => R)(implicit executor: ExecutionContext): Future[R]
A non-blocking, asynchronous left fold over the specified futures, with the start value of the given zero.
A non-blocking, asynchronous left fold over the specified futures, with the start value of the given zero. The fold is performed asynchronously in left-to-right order as the futures become completed. The result will be the first failure of any of the futures, or any failure in the actual fold, or the result of the fold.
Example:
val futureSum = Future.foldLeft(futures)(0)(_ + _)
- T
the type of the value of the input Futures
- R
the type of the value of the returned
Future
- futures
the
scala.collection.immutable.Iterable
of Futures to be folded- zero
the start value of the fold
- op
the fold operation to be applied to the zero and futures
- returns
the
Future
holding the result of the fold
- final def fromTry[T](result: Try[T]): Future[T]
Creates an already completed Future with the specified result or exception.
Creates an already completed Future with the specified result or exception.
- T
the type of the value in the
Future
- result
the result of the returned
Future
instance- returns
the newly created
Future
instance
- final def reduceLeft[T, R >: T](futures: collection.immutable.Iterable[Future[T]])(op: (R, T) => R)(implicit executor: ExecutionContext): Future[R]
Initiates a non-blocking, asynchronous, left reduction over the supplied futures where the zero is the result value of the first
Future
.Initiates a non-blocking, asynchronous, left reduction over the supplied futures where the zero is the result value of the first
Future
.Example:
val futureSum = Future.reduceLeft(futures)(_ + _)
- T
the type of the value of the input Futures
- R
the type of the value of the returned
Future
- futures
the
scala.collection.immutable.Iterable
of Futures to be reduced- op
the reduce operation which is applied to the results of the futures
- returns
the
Future
holding the result of the reduce
- final def sequence[A, CC[X] <: IterableOnce[X], To](in: CC[Future[A]])(implicit bf: BuildFrom[CC[Future[A]], A, To], executor: ExecutionContext): Future[To]
Simple version of
Future.traverse
.Simple version of
Future.traverse
. Asynchronously and non-blockingly transforms, in essence, aIterableOnce[Future[A]]
into aFuture[IterableOnce[A]]
. Useful for reducing manyFuture
s into a singleFuture
.- A
the type of the value inside the Futures
- CC
the type of the
IterableOnce
of Futures- To
the type of the resulting collection
- in
the
IterableOnce
of Futures which will be sequenced- returns
the
Future
of the resulting collection
- final def successful[T](result: T): Future[T]
Creates an already completed Future with the specified result.
Creates an already completed Future with the specified result.
- T
the type of the value in the future
- result
the given successful value
- returns
the newly created
Future
instance
- final def traverse[A, B, M[X] <: IterableOnce[X]](in: M[A])(fn: (A) => Future[B])(implicit bf: BuildFrom[M[A], B, M[B]], executor: ExecutionContext): Future[M[B]]
Asynchronously and non-blockingly transforms a
IterableOnce[A]
into aFuture[IterableOnce[B]]
using the provided functionA => Future[B]
.Asynchronously and non-blockingly transforms a
IterableOnce[A]
into aFuture[IterableOnce[B]]
using the provided functionA => Future[B]
. This is useful for performing a parallel map. For example, to apply a function to all items of a list in parallel:val myFutureList = Future.traverse(myList)(x => Future(myFunc(x)))
- A
the type of the value inside the Futures in the collection
- B
the type of the value of the returned
Future
- M
the type of the collection of Futures
- in
the collection to be mapped over with the provided function to produce a collection of Futures that is then sequenced into a Future collection
- fn
the function to be mapped over the collection to produce a collection of Futures
- returns
the
Future
of the collection of results
- final val unit: Future[Unit]
A Future which is completed with the Unit value.
- object never extends Future[Nothing]
A Future which is never completed.
Deprecated Value Members
- def fold[T, R](futures: IterableOnce[Future[T]])(zero: R)(op: (R, T) => R)(implicit executor: ExecutionContext): Future[R]
A non-blocking, asynchronous fold over the specified futures, with the start value of the given zero.
A non-blocking, asynchronous fold over the specified futures, with the start value of the given zero. The fold is performed on the thread where the last future is completed, the result will be the first failure of any of the futures, or any failure in the actual fold, or the result of the fold.
Example:
val futureSum = Future.fold(futures)(0)(_ + _)
- T
the type of the value of the input Futures
- R
the type of the value of the returned
Future
- futures
the
IterableOnce
of Futures to be folded- zero
the start value of the fold
- op
the fold operation to be applied to the zero and futures
- returns
the
Future
holding the result of the fold
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.0) use Future.foldLeft instead
- final def reduce[T, R >: T](futures: IterableOnce[Future[T]])(op: (R, T) => R)(implicit executor: ExecutionContext): Future[R]
Initiates a non-blocking, asynchronous, fold over the supplied futures where the fold-zero is the result value of the first
Future
in the collection.Initiates a non-blocking, asynchronous, fold over the supplied futures where the fold-zero is the result value of the first
Future
in the collection.Example:
val futureSum = Future.reduce(futures)(_ + _)
- T
the type of the value of the input Futures
- R
the type of the value of the returned
Future
- futures
the
IterableOnce
of Futures to be reduced- op
the reduce operation which is applied to the results of the futures
- returns
the
Future
holding the result of the reduce
- Annotations
- @deprecated
- Deprecated
(Since version 2.12.0) use Future.reduceLeft instead
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.collection.parallel
- Parallel collections (scala-parallel-collections.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.