Packages

abstract class Agent[T] extends AnyRef

The Agent class was inspired by agents in Clojure.

Agents provide asynchronous change of individual locations. Agents are bound to a single storage location for their lifetime, and only allow mutation of that location (to a new state) to occur as a result of an action. Update actions are functions that are asynchronously applied to the Agent's state and whose return value becomes the Agent's new state. The state of an Agent should be immutable.

While updates to Agents are asynchronous, the state of an Agent is always immediately available for reading by any thread (using get or apply) without any messages.

Agents are reactive. The update actions of all Agents get interleaved amongst threads in a thread pool. At any point in time, at most one send action for each Agent is being executed. Actions dispatched to an agent from another thread will occur in the order they were sent, potentially interleaved with actions dispatched to the same agent from other sources.

Example of usage:

val agent = Agent(5)

agent send (_ * 2)

...

val result = agent()
// use result ...

Agent is also monadic, which means that you can compose operations using for-comprehensions. In monadic usage the original agents are not touched but new agents are created. So the old values (agents) are still available as-is. They are so-called 'persistent'.

Example of monadic usage:

val agent1 = Agent(3)
val agent2 = Agent(5)

for (value <- agent1) {
  result = value + 1
}

val agent3 = for (value <- agent1) yield value + 1

val agent4 = for {
  value1 <- agent1
  value2 <- agent2
} yield value1 + value2

DEPRECATED STM SUPPORT

Agents participating in enclosing STM transaction is a deprecated feature in 2.3.

If an Agent is used within an enclosing transaction, then it will participate in that transaction. Agents are integrated with the STM - any dispatches made in a transaction are held until that transaction commits, and are discarded if it is retried or aborted.

Source
Agent.scala
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Instance Constructors

  1. new Agent()

Abstract Value Members

  1. abstract def alter(f: (T) ⇒ T): Future[T]

    Dispatch a function to update the internal state, and return a Future where that new state can be obtained.

    Dispatch a function to update the internal state, and return a Future where that new state can be obtained. In Java, pass in an instance of akka.dispatch.Mapper.

  2. abstract def alter(newValue: T): Future[T]

    Dispatch an update to the internal state, and return a Future where that new state can be obtained.

    Dispatch an update to the internal state, and return a Future where that new state can be obtained. In Java, pass in an instance of akka.dispatch.Mapper.

  3. abstract def alterOff(f: (T) ⇒ T)(implicit ec: ExecutionContext): Future[T]

    Dispatch a function to update the internal state but on its own thread, and return a Future where that new state can be obtained.

    Dispatch a function to update the internal state but on its own thread, and return a Future where that new state can be obtained. This does not use the reactive thread pool and can be used for long-running or blocking operations. Dispatches using either alterOff or alter will still be executed in order. In Java, pass in an instance of akka.dispatch.Mapper.

  4. abstract def flatMap[B](f: (T) ⇒ Agent[B]): Agent[B]

    Flatmap this agent to a new agent, applying the function to the internal state.

    Flatmap this agent to a new agent, applying the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Mapper.

  5. abstract def foreach[U](f: (T) ⇒ U): Unit

    Applies the function to the internal state.

    Applies the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Foreach.

  6. abstract def future(): Future[T]

    A future to the current value that will be completed after any currently queued updates.

  7. abstract def get(): T

    Java API: Read the internal state of the agent.

  8. abstract def map[B](f: (T) ⇒ B): Agent[B]

    Map this agent to a new agent, applying the function to the internal state.

    Map this agent to a new agent, applying the function to the internal state. Does not change the value of this agent. In Java, pass in an instance of akka.dispatch.Mapper.

  9. abstract def send(f: (T) ⇒ T): Unit

    Dispatch a function to update the internal state.

    Dispatch a function to update the internal state. In Java, pass in an instance of akka.dispatch.Mapper.

  10. abstract def send(newValue: T): Unit

    Dispatch a new value for the internal state.

    Dispatch a new value for the internal state. Behaves the same as sending a function (x => newValue).

  11. abstract def sendOff(f: (T) ⇒ T)(implicit ec: ExecutionContext): Unit

    Dispatch a function to update the internal state but on its own thread.

    Dispatch a function to update the internal state but on its own thread. This does not use the reactive thread pool and can be used for long-running or blocking operations. Dispatches using either sendOff or send will still be executed in order. In Java, pass in an instance of akka.dispatch.Mapper.

Concrete Value Members

  1. def apply(): T

    Read the internal state of the agent.