Akka. Is there a way to share code between two receives? - scala

Question

Let's say I have several receives and use become() unbecome() to switch between them. And all receives have some common message handling. Like this:
class Test extends Actor {
override def receive: Receive = first
def first: Receive = {
case "common" => // how to share?
println("common stuff")
case "second" =>
println("move to second")
context.become(second)
}
def second: Receive = {
case "common" => // how to share?
println("common stuff")
case "first" =>
println("move to first")
context.become(first)
}
}
Right now I see two ways:
Duplicate pattern match on "common" and
handle it in some function like handleCommon()
Merge receives like
this, but it doesn't seem right to me.
Here is an example of the second one:
class Test extends Actor {
override def receive: Receive = merge(common, first)
def common: Receive = {
case "common" =>
println("common stuff")
}
def first: Receive = {
case "second" =>
println("move to second")
context.become(merge(common, second))
}
def second: Receive = {
case "first" =>
println("move to first")
context.become(merge(common, first))
}
private def merge(functions: Receive*): Receive = {
case any =>
val fOpt = functions find (_.isDefinedAt(any))
if (fOpt.isDefined) {
fOpt foreach (f => f(any))
} else {
unhandled(any)
}
}
}
I'm sure there have to be a better way to do this. Is there?

Answer 1

You can use orElse:
def common: Receive = {
case "common" =>
println("common stuff")
}
def first: Receive = ({
case "second" =>
println("move to second")
context.become(second)
}: Receive) orElse common
def second: Receive = ({
case "first" =>
println("move to first")
context.become(first)
}: Receive) orElse common
Note that you have to explicitly annotate the type at the end of the expression because otherwise scala will infer Function1 and not Receive.