CanAsk

This class is used to establish a connection between a message class and the related response class using the ASK pattern. ask() requires a given instance of CanAsk. This ensures at COMPILE TIME that if ask() is called with a message of M, an instance of R (or a failed/cancelled IO) is guaranteed to be returned.

{{ sealed trait Message

case class MyMessage() extends Message case class MyOtherMessage() extends Message case class MyResponse()

given CanAsk[MyMessage, MyResponse] = canAsk

...

for myActor <- ... // spawn an Actor[Command] myResponse <- myActor ? MyMessage() // this will compile, as there is a given instance of // CanAsk[MyMessage, MyResponse]. The Compiler will also know // that myResponse os of type MyResponse, not generic type Response. myResponse <- myActor ? MyOtherMessage() // this will NOT compile, as there is no given instance of // CanAsk[MyOtherMessage, ?]. _ <- myActor ! MyOtherMessage() // this will compile, as TELL does not require any givens yield () }}