On 03/24/16 12:25, Mohammed Al-Mahfoudh wrote:
- If an ask statement, that sends a message /m1/ from /a1/ to /a2/
(actors), must /a2/ reply right away in the same "receive" invocation?
or we can have another /receive/ invocation reply to that ask? (I mean
by reply also resolving the future)
no, a2 does not need to reply immediately in the same receive
invocation. yes, another iteration of the receive loop can reply.
another actor even can reply to the future.
- How can that be implemented (abstractly speaking) since /a2/ doesn't
have an explicit handle for the Future object returned by the above ask?
when you call ask(), what happens under the covers is a temporary actor
is created as a mediator between a1 and a2. this temporary actor (call
it temp1) holds the future. when the message is sent from a1 to a2,
ask() actually sends the message to temp1, which then resends the
message. this is important, because it changes the sender address to
that of temp1, not a1. when a2 receives the message, sender() ==
temp1. when a2 replies, temp1 receives the message and completes the
future.
- Is there a "mapping" between which message sent back to /a1/
resolves which Future it asked for? If so, how to map that? (do you
encapsulate the original message /m1/ inside the later message sent
from a1 to a2 for replying, and then the ActorSystem knows how to
resolve that Future in the destination actor?)
no, there is no mapping. you have to do so yourself (if that is
important to you) by mapping the future returned from ask().
-Michael
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