object Future
- Alphabetic
- By Inheritance
- Future
- AnyRef
- Any
- Hide All
- Show All
- Public
- All
Value Members
- final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- AnyRef → Any
- final def ##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
- final def ==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- AnyRef → Any
- 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 asInstanceOf[T0]: T0
Cast the receiver object to be of type
T0
.Cast the receiver object to be of type
T0
.Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression
1.asInstanceOf[String]
will throw aClassCastException
at runtime, while the expressionList(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver object is not an instance of the erasure of typeT0
.
- def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the
clone
method is platform dependent.- returns
a copy of the receiver object.
- 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 eq(arg0: AnyRef): Boolean
Tests whether the argument (
that
) is a reference to the receiver object (this
).Tests whether the argument (
that
) is a reference to the receiver object (this
).The
eq
method implements an equivalence relation on non-null instances ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2
), they should be equal to each other (o1 == o2
) and they should hash to the same value (o1.hashCode == o2.hashCode
).- returns
true
if the argument is a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
- It is consistent: for any non-null instances
- def equals(arg0: AnyRef): Boolean
The equality method for reference types.
- 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
- def finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the
finalize
method is invoked, as well as the interaction betweenfinalize
and non-local returns and exceptions, are all platform dependent. - 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 getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
- def hashCode(): Int
The hashCode method for reference types.
- final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is
T0
.Test whether the dynamic type of the receiver object is
T0
.Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression
1.isInstanceOf[String]
will returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
- final def ne(arg0: AnyRef): Boolean
Equivalent to
!(this eq that)
.Equivalent to
!(this eq that)
.- returns
true
if the argument is not a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
- final def notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
- final def notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
- 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 synchronized[T0](arg0: => T0): T0
- Definition Classes
- AnyRef
- def toString(): String
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
- returns
a String representation of the object.
- Definition Classes
- AnyRef → Any
- 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.
- final def wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- final def wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- final def wait(arg0: Long): Unit
- 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
.