Merge pull request #25137 from akka/wip-24856-EventHandler-alias-patriknw
add EventHandler type alias, #24856
This commit is contained in:
Patrik Nordwall
GitHub
commit
7f8f3c122b
5 changed files with 69 additions and 36 deletions
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@ -29,7 +29,7 @@ private[persistence] final class EventsourcedSetup[C, E, S](
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val persistenceId: String,
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val emptyState: S,
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val commandHandler: PersistentBehaviors.CommandHandler[C, E, S],
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val eventHandler: (S, E) ⇒ S,
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val eventHandler: PersistentBehaviors.EventHandler[S, E],
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val writerIdentity: WriterIdentity,
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val recoveryCompleted: (ActorContext[C], S) ⇒ Unit,
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val onSnapshot: (ActorContext[C], SnapshotMetadata, Try[Done]) ⇒ Unit,
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@ -35,7 +35,7 @@ private[akka] final case class PersistentBehaviorImpl[Command, Event, State](
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persistenceId: String,
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emptyState: State,
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commandHandler: PersistentBehaviors.CommandHandler[Command, Event, State],
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eventHandler: (State, Event) ⇒ State,
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eventHandler: PersistentBehaviors.EventHandler[State, Event],
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journalPluginId: Option[String] = None,
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snapshotPluginId: Option[String] = None,
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recoveryCompleted: (ActorContext[Command], State) ⇒ Unit = ConstantFun.scalaAnyTwoToUnit,
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@ -16,24 +16,47 @@ import scala.util.Try
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object PersistentBehaviors {
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// we use this type internally, however it's easier for users to understand the function, so we use it in external api
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/**
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* Type alias for the command handler function for reacting on events having been persisted.
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*
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* The type alias is not used in API signatures because it's easier to see (in IDE) what is needed
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* when full function type is used. When defining the handler as a separate function value it can
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* be useful to use the alias for shorter type signature.
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*/
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type CommandHandler[Command, Event, State] = (ActorContext[Command], State, Command) ⇒ Effect[Event, State]
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/**
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* Type alias for the event handler function defines how to act on commands.
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*
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* The type alias is not used in API signatures because it's easier to see (in IDE) what is needed
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* when full function type is used. When defining the handler as a separate function value it can
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* be useful to use the alias for shorter type signature.
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*/
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type EventHandler[State, Event] = (State, Event) ⇒ State
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/**
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* Create a `Behavior` for a persistent actor.
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*/
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def receive[Command, Event, State](
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persistenceId: String,
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emptyState: State,
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commandHandler: CommandHandler[Command, Event, State],
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commandHandler: (ActorContext[Command], State, Command) ⇒ Effect[Event, State],
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eventHandler: (State, Event) ⇒ State): PersistentBehavior[Command, Event, State] =
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PersistentBehaviorImpl(persistenceId, emptyState, commandHandler, eventHandler)
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/**
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* The `CommandHandler` defines how to act on commands.
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* The `CommandHandler` defines how to act on commands. A `CommandHandler` is
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* a function:
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*
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* {{{
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* (ActorContext[Command], State, Command) ⇒ Effect[Event, State]
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* }}}
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*
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* Note that you can have different command handlers based on current state by using
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* [[CommandHandler#byState]].
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*
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* The [[CommandHandler#command]] is useful for simple commands that don't need the state
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* and context.
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*/
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object CommandHandler {
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@ -42,14 +65,16 @@ object PersistentBehaviors {
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*
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* @see [[Effect]] for possible effects of a command.
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*/
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def command[Command, Event, State](commandHandler: Command ⇒ Effect[Event, State]): CommandHandler[Command, Event, State] =
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def command[Command, Event, State](commandHandler: Command ⇒ Effect[Event, State]): (ActorContext[Command], State, Command) ⇒ Effect[Event, State] =
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(_, _, cmd) ⇒ commandHandler(cmd)
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/**
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* Select different command handlers based on current state.
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*/
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def byState[Command, Event, State](choice: State ⇒ CommandHandler[Command, Event, State]): CommandHandler[Command, Event, State] =
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def byState[Command, Event, State](
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choice: State ⇒ (ActorContext[Command], State, Command) ⇒ Effect[Event, State]): (ActorContext[Command], State, Command) ⇒ Effect[Event, State] = {
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new ByStateCommandHandler(choice)
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}
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}
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@ -36,7 +36,7 @@ object PersistentActorCompileOnlyTest {
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//#command-handler
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//#event-handler
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val eventHandler: (ExampleState, SimpleEvent) ⇒ (ExampleState) = {
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val eventHandler: (ExampleState, SimpleEvent) ⇒ ExampleState = {
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case (state, Evt(data)) ⇒ state.copy(data :: state.events)
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}
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//#event-handler
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@ -341,30 +341,35 @@ object PersistentActorCompileOnlyTest {
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if (currentState == newMood) Effect.none
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else Effect.persist(MoodChanged(newMood))
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val commandHandler: CommandHandler[Command, Event, Mood] = { (_, state, cmd) ⇒
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cmd match {
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case Greet(whom) ⇒
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println(s"Hi there, I'm $state!")
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Effect.none
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case CheerUp(sender) ⇒
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changeMoodIfNeeded(state, Happy)
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.andThen {
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sender ! Ack
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}
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case Remember(memory) ⇒
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// A more elaborate example to show we still have full control over the effects
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// if needed (e.g. when some logic is factored out but you want to add more effects)
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val commonEffects: Effect[Event, Mood] = changeMoodIfNeeded(state, Happy)
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Effect.persist(commonEffects.events :+ Remembered(memory), commonEffects.sideEffects)
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}
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}
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private val eventHandler: EventHandler[Mood, Event] = {
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case (_, MoodChanged(to)) ⇒ to
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case (state, Remembered(_)) ⇒ state
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}
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PersistentBehaviors.receive[Command, Event, Mood](
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persistenceId = "myPersistenceId",
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emptyState = Sad,
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commandHandler = (_, state, cmd) ⇒
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cmd match {
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case Greet(whom) ⇒
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println(s"Hi there, I'm $state!")
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Effect.none
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case CheerUp(sender) ⇒
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changeMoodIfNeeded(state, Happy)
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.andThen {
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sender ! Ack
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}
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case Remember(memory) ⇒
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// A more elaborate example to show we still have full control over the effects
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// if needed (e.g. when some logic is factored out but you want to add more effects)
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val commonEffects: Effect[Event, Mood] = changeMoodIfNeeded(state, Happy)
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Effect.persist(commonEffects.events :+ Remembered(memory), commonEffects.sideEffects)
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},
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eventHandler = {
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case (_, MoodChanged(to)) ⇒ to
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case (state, Remembered(_)) ⇒ state
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})
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commandHandler,
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eventHandler)
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}
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@ -5,6 +5,7 @@
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package docs.akka.persistence.typed
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import akka.Done
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import akka.actor.typed.scaladsl.ActorContext
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import akka.actor.typed.{ ActorRef, Behavior }
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import akka.persistence.typed.scaladsl.PersistentBehaviors
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import akka.persistence.typed.scaladsl.PersistentBehaviors.CommandHandler
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@ -52,7 +53,7 @@ object InDepthPersistentBehaviorSpec {
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//#commands
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//#initial-command-handler
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private def initial: CommandHandler[BlogCommand, BlogEvent, BlogState] =
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private val initial: (ActorContext[BlogCommand], BlogState, BlogCommand) ⇒ Effect[BlogEvent, BlogState] =
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(ctx, state, cmd) ⇒
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cmd match {
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case AddPost(content, replyTo) ⇒
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@ -69,7 +70,7 @@ object InDepthPersistentBehaviorSpec {
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//#initial-command-handler
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//#post-added-command-handler
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private def postAdded: CommandHandler[BlogCommand, BlogEvent, BlogState] = {
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private val postAdded: (ActorContext[BlogCommand], BlogState, BlogCommand) ⇒ Effect[BlogEvent, BlogState] = {
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(ctx, state, cmd) ⇒
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cmd match {
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case ChangeBody(newBody, replyTo) ⇒
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@ -94,14 +95,15 @@ object InDepthPersistentBehaviorSpec {
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//#post-added-command-handler
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//#by-state-command-handler
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private def commandHandler: CommandHandler[BlogCommand, BlogEvent, BlogState] = CommandHandler.byState {
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case state if state.isEmpty ⇒ initial
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case state if !state.isEmpty ⇒ postAdded
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}
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private val commandHandler: (ActorContext[BlogCommand], BlogState, BlogCommand) ⇒ Effect[BlogEvent, BlogState] =
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CommandHandler.byState {
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case state if state.isEmpty ⇒ initial
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case state if !state.isEmpty ⇒ postAdded
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}
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//#by-state-command-handler
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//#event-handler
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private def eventHandler(state: BlogState, event: BlogEvent): BlogState =
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private val eventHandler: (BlogState, BlogEvent) ⇒ BlogState = { (state, event) ⇒
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event match {
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case PostAdded(postId, content) ⇒
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state.withContent(content)
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@ -115,6 +117,7 @@ object InDepthPersistentBehaviorSpec {
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case Published(_) ⇒
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state.copy(published = true)
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}
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}
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//#event-handler
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//#behavior
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