Why is Actor.receive a partial function?

Question

Why is Actor.receive a partial function? I can always have a regular function with match expression instead of it.

Answer 1

It is a PartialFunction to capture the possibility of a message being handled or unhandled by the Actor. An unhandled message will

1. not make the Actor fail with a MatchError
2. spawn an UnhandledMessage event to the event stream

More info here.

Answer 2

One reason would be that the partial function has isDefinedAt method, which allows Akka to check if the message can be handled without catching the scala.MatchError exception from user's code.