Scala Standard Library 2.12.2 - scala.concurrent.Future.never

final def !=(arg0: Any): Boolean

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 and null.

Equivalent to x.hashCode except for boxed numeric types and null. 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. For null returns a hashcode where null.hashCode throws a NullPointerException.

returns: a hash value consistent with ==

Definition Classes: AnyRef → Any

final def ==(arg0: Any): Boolean

The expression x == that is equivalent to if (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

def andThen[U](pf: PartialFunction[Try[Nothing], U])(implicit executor: ExecutionContext): Future[Nothing]

Applies the side-effecting function to the result of this future, and returns a new future with the result of this future.

This method allows one to enforce that the callbacks are executed in a specified order.

Note that if one of the chained andThen callbacks throws an exception, that exception is not propagated to the subsequent andThen callbacks. Instead, the subsequent andThen callbacks are given the original value of this future.

The following example prints out 5:

val f = Future { 5 }
f andThen {
  case r => sys.error("runtime exception")
} andThen {
  case Failure(t) => println(t)
  case Success(v) => println(v)
}

Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the ExecutionContext.

U: only used to accept any return type of the given PartialFunction
pf: a PartialFunction which will be conditionally applied to the outcome of this Future
returns: a Future which will be completed with the exact same outcome as this Future but after the PartialFunction has been executed.

Definition Classes: never → Future

final def asInstanceOf[T0]: 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 a ClassCastException at runtime, while the expression List(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 type T0.

def clone(): AnyRef

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

returns: a copy of the receiver object.

Attributes: protected[java.lang]
Definition Classes: AnyRef
Annotations: @throws( ... )
Note: not specified by SLS as a member of AnyRef

def collect[S](pf: PartialFunction[Nothing, S])(implicit executor: ExecutionContext): Future[S]

Creates a new future by mapping the value of the current future, if the given partial function is defined at that value.

If the current future contains a value for which the partial function is defined, the new future will also hold that value. Otherwise, the resulting future will fail with a NoSuchElementException.

If the current future fails, then the resulting future also fails.

Example:

val f = Future { -5 }
val g = f collect {
  case x if x < 0 => -x
}
val h = f collect {
  case x if x > 0 => x * 2
}
g foreach println // Eventually prints 5
Await.result(h, Duration.Zero) // throw a NoSuchElementException

S: the type of the returned Future
pf: the PartialFunction to apply to the successful result of this Future
returns: a Future holding the result of application of the PartialFunction or a NoSuchElementException

Definition Classes: never → Future

final def eq(arg0: AnyRef): Boolean

Tests whether the argument (that) is a reference to the receiver object (this).

The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
null.eq(null) returns true.

When overriding the equals or hashCode 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

def equals(arg0: Any): Boolean

The equality method for reference types.

The equality method for reference types. Default implementation delegates to eq.

See also equals in scala.Any.

returns: true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes: AnyRef → Any

def failed: Future[Throwable]

The returned Future will be successfully completed with the Throwable of the original Future if the original Future fails.

If the original Future is successful, the returned Future is failed with a NoSuchElementException.

returns: a failed projection of this Future.

Definition Classes: never → Future

def fallbackTo[U](that: Future[U]): Future[U]

Creates a new future which holds the result of this future if it was completed successfully, or, if not, the result of the that future if that is completed successfully.

Creates a new future which holds the result of this future if it was completed successfully, or, if not, the result of the that future if that is completed successfully. If both futures are failed, the resulting future holds the throwable object of the first future.

Using this method will not cause concurrent programs to become nondeterministic.

Example:

val f = Future { sys.error("failed") }
val g = Future { 5 }
val h = f fallbackTo g
h foreach println // Eventually prints 5

U: the type of the other Future and the resulting Future
that: the Future whose result we want to use if this Future fails.
returns: a Future with the successful result of this or that Future or the failure of this Future if both fail

Definition Classes: never → Future

def filter(p: (Nothing) ⇒ Boolean)(implicit executor: ExecutionContext): Future[Nothing]

Creates a new future by filtering the value of the current future with a predicate.

If the current future contains a value which satisfies the predicate, the new future will also hold that value. Otherwise, the resulting future will fail with a NoSuchElementException.

If the current future fails, then the resulting future also fails.

Example:

val f = Future { 5 }
val g = f filter { _ % 2 == 1 }
val h = f filter { _ % 2 == 0 }
g foreach println // Eventually prints 5
Await.result(h, Duration.Zero) // throw a NoSuchElementException

p: the predicate to apply to the successful result of this Future
returns: a Future which will hold the successful result of this Future if it matches the predicate or a NoSuchElementException

Definition Classes: never → Future

def finalize(): Unit

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 between finalize and non-local returns and exceptions, are all platform dependent.

Attributes: protected[java.lang]
Definition Classes: AnyRef
Annotations: @throws( classOf[java.lang.Throwable] )
Note: not specified by SLS as a member of AnyRef

def flatMap[S](f: (Nothing) ⇒ Future[S])(implicit executor: ExecutionContext): Future[S]

Creates a new future by applying a function to the successful result of this future, and returns the result of the function as the new future.

Creates a new future by applying a function to the successful result of this future, and returns the result of the function as the new future. If this future is completed with an exception then the new future will also contain this exception.

Example:

val f = Future { 5 }
val g = Future { 3 }
val h = for {
  x: Int <- f // returns Future(5)
  y: Int <- g // returns Future(3)
} yield x + y

is translated to:

f flatMap { (x: Int) => g map { (y: Int) => x + y } }

S: the type of the returned Future
f: the function which will be applied to the successful result of this Future
returns: a Future which will be completed with the result of the application of the function

Definition Classes: never → Future

def flatten[S](implicit ev: <:<[Nothing, Future[S]]): Future[S]

Creates a new future with one level of nesting flattened, this method is equivalent to flatMap(identity).

S: the type of the returned Future

Definition Classes: never → Future

def foreach[U](f: (Nothing) ⇒ U)(implicit executor: ExecutionContext): Unit

Asynchronously processes the value in the future once the value becomes available.

WARNING: Will not be called if this future is never completed or if it is completed with a failure.

Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the ExecutionContext.

U: only used to accept any return type of the given callback function
f: the function which will be executed if this Future completes with a result, the return value of f will be discarded.

Definition Classes: never → Future

final def getClass(): Class[_]

Returns the runtime class representation of the object.

returns: a class object corresponding to the runtime type of the receiver.

Definition Classes: AnyRef → Any

def hashCode(): Int

The hashCode method for reference types.

The hashCode method for reference types. See hashCode in scala.Any.

returns: the hash code value for this object.

Definition Classes: AnyRef → Any

def isCompleted: Boolean

Returns whether the future had already been completed with a value or an exception.

Note: using this method yields nondeterministic dataflow programs.

returns: true if the future was completed, false otherwise

Definition Classes: never → Future

final def isInstanceOf[T0]: Boolean

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 return false, while the expression List(1).isInstanceOf[List[String]] will return true. 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 type T0; false otherwise.

Definition Classes: Any

def map[S](f: (Nothing) ⇒ S)(implicit executor: ExecutionContext): Future[S]

Creates a new future by applying a function to the successful result of this future.

Creates a new future by applying a function to the successful result of this future. If this future is completed with an exception then the new future will also contain this exception.

Example:

val f = Future { "The future" }
val g = f map { x: String => x + " is now!" }

Note that a for comprehension involving a Future may expand to include a call to map and or flatMap and withFilter. See scala.concurrent.Future#flatMap for an example of such a comprehension.

S: the type of the returned Future
f: the function which will be applied to the successful result of this Future
returns: a Future which will be completed with the result of the application of the function

Definition Classes: never → Future

def mapTo[S](implicit tag: ClassTag[S]): Future[S]

Creates a new Future[S] which is completed with this Future's result if that conforms to S's erased type or a ClassCastException otherwise.

S: the type of the returned Future
tag: the ClassTag which will be used to cast the result of this Future
returns: a Future holding the casted result of this Future or a ClassCastException otherwise

Definition Classes: never → Future

final def ne(arg0: AnyRef): Boolean

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.

Definition Classes: AnyRef
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.

Definition Classes: AnyRef
Note: not specified by SLS as a member of AnyRef

def onComplete[U](f: (Try[Nothing]) ⇒ U)(implicit executor: ExecutionContext): Unit

When this future is completed, either through an exception, or a value, apply the provided function.

If the future has already been completed, this will either be applied immediately or be scheduled asynchronously.

Note that the returned value of f will be discarded.

Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the ExecutionContext.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously. Completion of the Future must *happen-before* the invocation of the callback.

U: only used to accept any return type of the given callback function
f: the function to be executed when this Future completes

Definition Classes: never → Future

def onFailure[U](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Unit

When this future is completed with a failure (i.e., with a throwable), apply the provided callback to the throwable.

The future may contain a throwable object and this means that the future failed. Futures obtained through combinators have the same exception as the future they were obtained from. The following throwable objects are not contained in the future:

Error - errors are not contained within futures
InterruptedException - not contained within futures
all scala.util.control.ControlThrowable except NonLocalReturnControl - not contained within futures

Instead, the future is completed with a ExecutionException with one of the exceptions above as the cause. If a future is failed with a scala.runtime.NonLocalReturnControl, it is completed with a value from that throwable instead.

If the future has already been completed with a failure, this will either be applied immediately or be scheduled asynchronously.

Will not be called in case that the future is completed with a value.

Note that the returned value of pf will be discarded.

Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the ExecutionContext.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously. Completion of the Future must *happen-before* the invocation of the callback.

Definition Classes: never → Future

def onSuccess[U](pf: PartialFunction[Nothing, U])(implicit executor: ExecutionContext): Unit

When this future is completed successfully (i.e., with a value), apply the provided partial function to the value if the partial function is defined at that value.

If the future has already been completed with a value, this will either be applied immediately or be scheduled asynchronously.

Note that the returned value of pf will be discarded.

Since this method executes asynchronously and does not produce a return value, any non-fatal exceptions thrown will be reported to the ExecutionContext.

Multiple callbacks may be registered; there is no guarantee that they will be executed in a particular order.

The provided callback always runs in the provided implicit ExecutionContext, though there is no guarantee that the execute() method on the ExecutionContext will be called once per callback or that execute() will be called in the current thread. That is, the implementation may run multiple callbacks in a batch within a single execute() and it may run execute() either immediately or asynchronously. Completion of the Future must *happen-before* the invocation of the callback.

Definition Classes: never → Future

def ready(atMost: Duration)(implicit permit: CanAwait): never.this.type

Await the "completed" state of this Awaitable.

This method should not be called directly; use Await.ready instead.

atMost: maximum wait time, which may be negative (no waiting is done), Duration.Inf for unbounded waiting, or a finite positive duration
returns: this Awaitable

Definition Classes: never → Awaitable
Annotations: @throws( clazz = classOf[TimeoutException] ) @throws( clazz = classOf[InterruptedException] )
Exceptions thrown: IllegalArgumentException if atMost is Duration.Undefined
InterruptedException if the current thread is interrupted while waiting
TimeoutException if after waiting for the specified time this Awaitable is still not ready

def recover[U](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Future[U]

Creates a new future that will handle any matching throwable that this future might contain.

Creates a new future that will handle any matching throwable that this future might contain. If there is no match, or if this future contains a valid result then the new future will contain the same.

Example:

Future (6 / 0) recover { case e: ArithmeticException => 0 } // result: 0
Future (6 / 0) recover { case e: NotFoundException   => 0 } // result: exception
Future (6 / 2) recover { case e: ArithmeticException => 0 } // result: 3

U: the type of the returned Future
pf: the PartialFunction to apply if this Future fails
returns: a Future with the successful value of this Future or the result of the PartialFunction

Definition Classes: never → Future

def recoverWith[U](pf: PartialFunction[Throwable, Future[U]])(implicit executor: ExecutionContext): Future[U]

Creates a new future that will handle any matching throwable that this future might contain by assigning it a value of another future.

If there is no match, or if this future contains a valid result then the new future will contain the same result.

Example:

val f = Future { Int.MaxValue }
Future (6 / 0) recoverWith { case e: ArithmeticException => f } // result: Int.MaxValue

U: the type of the returned Future
pf: the PartialFunction to apply if this Future fails
returns: a Future with the successful value of this Future or the outcome of the Future returned by the PartialFunction

Definition Classes: never → Future

def result(atMost: Duration)(implicit permit: CanAwait): Nothing

Await and return the result (of type T) of this Awaitable.

This method should not be called directly; use Await.result instead.

atMost: maximum wait time, which may be negative (no waiting is done), Duration.Inf for unbounded waiting, or a finite positive duration
returns: the result value if the Awaitable is completed within the specific maximum wait time

Definition Classes: never → Awaitable
Annotations: @throws( clazz = classOf[Exception] )
Exceptions thrown: IllegalArgumentException if atMost is Duration.Undefined
InterruptedException if the current thread is interrupted while waiting
TimeoutException if after waiting for the specified time this Awaitable is still not ready

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: never → AnyRef → Any

def transform[S](f: (Try[Nothing]) ⇒ Try[S])(implicit executor: ExecutionContext): Future[S]

Creates a new Future by applying the specified function to the result of this Future.

Creates a new Future by applying the specified function to the result of this Future. If there is any non-fatal exception thrown when 'f' is applied then that exception will be propagated to the resulting future.

S: the type of the returned Future
f: function that transforms the result of this future
returns: a Future that will be completed with the transformed value

Definition Classes: never → Future

def transform[S](s: (Nothing) ⇒ S, f: (Throwable) ⇒ Throwable)(implicit executor: ExecutionContext): Future[S]

Creates a new future by applying the 's' function to the successful result of this future, or the 'f' function to the failed result.

Creates a new future by applying the 's' function to the successful result of this future, or the 'f' function to the failed result. If there is any non-fatal exception thrown when 's' or 'f' is applied, that exception will be propagated to the resulting future.

S: the type of the returned Future
s: function that transforms a successful result of the receiver into a successful result of the returned future
f: function that transforms a failure of the receiver into a failure of the returned future
returns: a Future that will be completed with the transformed value

Definition Classes: never → Future

def transformWith[S](f: (Try[Nothing]) ⇒ Future[S])(implicit executor: ExecutionContext): Future[S]

Creates a new Future by applying the specified function, which produces a Future, to the result of this Future.

Creates a new Future by applying the specified function, which produces a Future, to the result of this Future. If there is any non-fatal exception thrown when 'f' is applied then that exception will be propagated to the resulting future.

S: the type of the returned Future
f: function that transforms the result of this future
returns: a Future that will be completed with the transformed value

Definition Classes: never → Future

def value: Option[Try[Nothing]]

The current value of this Future.

Note: using this method yields nondeterministic dataflow programs.

If the future was not completed the returned value will be None. If the future was completed the value will be Some(Success(t)) if it contained a valid result, or Some(Failure(error)) if it contained an exception.

returns: None if the Future wasn't completed, Some if it was.

Definition Classes: never → Future

final def wait(): Unit

Definition Classes: AnyRef
Annotations: @throws( ... )

final def wait(arg0: Long, arg1: Int): Unit

Definition Classes: AnyRef
Annotations: @throws( ... )

final def wait(arg0: Long): Unit

Definition Classes: AnyRef
Annotations: @throws( ... )

final def withFilter(p: (Nothing) ⇒ Boolean)(implicit executor: ExecutionContext): Future[Nothing]

Used by for-comprehensions.

Definition Classes: Future

def zip[U](that: Future[U]): Future[(Nothing, U)]

Zips the values of this and that future, and creates a new future holding the tuple of their results.

If this future fails, the resulting future is failed with the throwable stored in this. Otherwise, if that future fails, the resulting future is failed with the throwable stored in that.

U: the type of the other Future
that: the other Future
returns: a Future with the results of both futures or the failure of the first of them that failed

Definition Classes: never → Future

def zipWith[U, R](that: Future[U])(f: (Nothing, U) ⇒ R)(implicit executor: ExecutionContext): Future[R]

Zips the values of this and that future using a function f, and creates a new future holding the result.

If this future fails, the resulting future is failed with the throwable stored in this. Otherwise, if that future fails, the resulting future is failed with the throwable stored in that. If the application of f throws a throwable, the resulting future is failed with that throwable if it is non-fatal.

U: the type of the other Future
R: the type of the resulting Future
that: the other Future
f: the function to apply to the results of this and that
returns: a Future with the result of the application of f to the results of this and that

Definition Classes: never → Future

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

never

object never extends Future[Nothing]

Value Members

Inherited from Future[Nothing]

Inherited from Awaitable[Nothing]

Inherited from AnyRef

Inherited from Any

Callbacks

Polling

Transformations

Ungrouped

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

never 

object never extends Future[Nothing]

Value Members

Inherited from Future[Nothing]

Inherited from Awaitable[Nothing]

Inherited from AnyRef

Inherited from Any

Callbacks

Polling

Transformations

Ungrouped

never