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Reword the "ask versus ?" typed style docs (#27390)

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Dale Wijnand 2019-07-23 08:25:34 +01:00 • committed by Arnout Engelen
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11
akka-docs/src/main/paradox/typed/style-guide.md
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@ -409,29 +409,28 @@ Scala
## ask versus ?
When using the `AskPattern` it's recommended to use the `ask` method rather than the `?` operator.
When using the `AskPattern` it's recommended to use the `ask` method rather than the infix `?` operator, like so:
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #ask-1 }
Instead of the `replyTo` you can use `_` for less verbosity.
You may also use the more terse placeholder syntax `_` instead of `replyTo`:
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #ask-2 }
When using `?` the following doesn't compile because of type inference problem:
However, using the infix operator `?` with the placeholder syntax `_`, like is done in the following example, won't typecheck because of the binding scope rules for wildcard parameters:
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #ask-3 }
By adding parentheses it works but is rather ugly, and therefore better to stick with `ask`.
Adding the necessary parentheses (as shown below) makes it typecheck, but, subjectively, it's rather ugly so the recommendation is to use `ask`.
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #ask-4 }
Note that `AskPattern` is only intended for request-response interaction from outside an actor. If the requester is
inside an actor, prefer `ActorContext.ask` as it provides better thread-safety by not involving
@scala[`Future`]@java[`CompletionStage`] inside the actor.
inside an actor, prefer `ActorContext.ask` as it provides better thread-safety by not requiring the use of a @scala[`Future`]@java[`CompletionStage`] inside the actor.
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