final class MVar[F[_], A] extends MVar2[F, A]
A mutable location, that is either empty or contains
a value of type A.
It has the following fundamental atomic operations:
- put which fills the var if empty, or blocks (asynchronously) until the var is empty again
- tryPut which fills the var if empty. returns true if successful
- take which empties the var if full, returning the contained value, or blocks (asynchronously) otherwise until there is a value to pull
- tryTake empties if full, returns None if empty.
- read which reads the current value without touching it,
assuming there is one, or otherwise it waits until a value
is made available via
put - tryRead returns
Some(a)if full, without modifying the var, or else returnsNone - isEmpty returns true if currently empty
The MVar is appropriate for building synchronization
primitives and performing simple inter-thread communications.
If it helps, it's similar with a BlockingQueue(capacity = 1),
except that it is pure and that doesn't block any threads, all
waiting being done asynchronously.
Given its asynchronous, non-blocking nature, it can be used on top of Javascript as well.
N.B. this is a reimplementation of the interface exposed in Cats-Effect, see: cats.effect.concurrent.MVar
Inspired by Control.Concurrent.MVar from Haskell.
- Source
- MVar.scala
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- def imapK[G[_]](f: ~>[F, G], g: ~>[G, F]): MVar2[G, A]
- Definition Classes
- MVar2
- def isEmpty: F[Boolean]
Returns
trueif the var is empty,falseif full.Returns
trueif the var is empty,falseif full.- Definition Classes
- MVar → MVar
- final def isInstanceOf[T0]: Boolean
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- def modify[B](f: (A) => F[(A, B)]): F[B]
Modifies the contents of the
MVarusing the effectful functionf, but also allows for returning a value derived from the original contents of theMVar.Modifies the contents of the
MVarusing the effectful functionf, but also allows for returning a value derived from the original contents of theMVar. Like use, in case of failure, it sets the contents of theMVarto the original value.- f
effectful function that operates on the contents of this
MVar- returns
the second value produced by applying
fto the contents of thisMVar
- Definition Classes
- MVar → MVar2
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar.
- def modify_(f: (A) => F[A]): F[Unit]
Modifies the contents of the
MVarusing the effectful functionf.Modifies the contents of the
MVarusing the effectful functionf. Like use, in case of failure, it sets the contents of theMVarto the original value.- f
effectful function that operates on the contents of this
MVar- returns
no useful value. Executed only for the effects.
- Definition Classes
- MVar → MVar2
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar.
- final def ne(arg0: AnyRef): Boolean
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- final def notify(): Unit
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- final def notifyAll(): Unit
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- def put(a: A): F[Unit]
Fills the
MVarif it is empty, or blocks (asynchronously) if theMVaris full, until the given value is next in line to be consumed on take.Fills the
MVarif it is empty, or blocks (asynchronously) if theMVaris full, until the given value is next in line to be consumed on take.This operation is atomic.
- returns
a task that on evaluation will complete when the
putoperation succeeds in filling theMVar, with the given value being next in line to be consumed
- Definition Classes
- MVar → MVar
- def read: F[A]
Tries reading the current value, or blocks (asynchronously) until there is a value available.
Tries reading the current value, or blocks (asynchronously) until there is a value available.
This operation is atomic.
- returns
a task that on evaluation will be completed after a value has been read
- Definition Classes
- MVar → MVar
- def swap(newValue: A): F[A]
Replaces a value in MVar and returns the old value.
Replaces a value in MVar and returns the old value.
- newValue
is a new value
- returns
the value taken
- Definition Classes
- MVar → MVar2
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar.
- final def synchronized[T0](arg0: => T0): T0
- Definition Classes
- AnyRef
- def take: F[A]
Empties the
MVarif full, returning the contained value, or blocks (asynchronously) until a value is available.Empties the
MVarif full, returning the contained value, or blocks (asynchronously) until a value is available.This operation is atomic.
- returns
a task that on evaluation will be completed after a value was retrieved
- Definition Classes
- MVar → MVar
- def toString(): String
- Definition Classes
- AnyRef → Any
- def tryPut(a: A): F[Boolean]
Fill the
MVarif we can do it without blocking,Fill the
MVarif we can do it without blocking,- returns
whether or not the put succeeded
- Definition Classes
- MVar → MVar
- def tryRead: F[Option[A]]
Tries reading the current value, returning
Some(a)if the var is full, but without modifying the var in any way.Tries reading the current value, returning
Some(a)if the var is full, but without modifying the var in any way. OrNoneif the var is empty.- Definition Classes
- MVar → MVar2
- def tryTake: F[Option[A]]
Empty the
MVarif fullEmpty the
MVarif full- returns
an Option holding the current value, None means it was empty
- Definition Classes
- MVar → MVar
- def use[B](f: (A) => F[B]): F[B]
Applies the effectful function
fon the contents of thisMVar.Applies the effectful function
fon the contents of thisMVar. In case of failure, it sets the contents of theMVarto the original value.- f
effectful function that operates on the contents of this
MVar- returns
the value produced by applying
fto the contents of thisMVar
- Definition Classes
- MVar → MVar2
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar.
- final def wait(arg0: Long, arg1: Int): Unit
- Definition Classes
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- Annotations
- @throws(classOf[java.lang.InterruptedException])
- final def wait(arg0: Long): Unit
- Definition Classes
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- @throws(classOf[java.lang.InterruptedException]) @native()
- final def wait(): Unit
- Definition Classes
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- @throws(classOf[java.lang.InterruptedException])
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- def finalize(): Unit
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- Deprecated
- def mapK[G[_]](f: ~>[F, G]): cats.effect.concurrent.MVar[G, A]
- Definition Classes
- MVar
- Annotations
- @deprecated
- Deprecated
(Since version 2.2.0)
mapKis deprecated in favor ofimapKwhich supports the new invariantMVar2interface
This is the API documentation for the Monix library.
Package Overview
monix.execution exposes lower level primitives for dealing with asynchronous execution:
Atomictypes, as alternative tojava.util.concurrent.atomicmonix.catnap exposes pure abstractions built on top of the Cats-Effect type classes:
monix.eval is for dealing with evaluation of results, thus exposing Task and Coeval.
monix.reactive exposes the
Observablepattern:Observableimplementationsmonix.tail exposes Iterant for purely functional pull based streaming:
BatchandBatchCursor, the alternatives to Scala'sIterableandIteratorrespectively that we are using within Iterant's encodingYou can control evaluation with type you choose - be it Task, Coeval, cats.effect.IO or your own as long as you provide correct cats-effect or cats typeclass instance.