MailboxProcessor.PostAndTryAsyncReply<'Msg,'Reply> Method (F#)
Like MailboxProcessor.AsyncPostAndReply, but returns None if no reply within the timeout period.
Namespace/Module Path: Microsoft.FSharp.Control
Assembly: FSharp.Core (in FSharp.Core.dll)
Syntax
// Signature:
member this.PostAndTryAsyncReply : (AsyncReplyChannel<'Reply> -> 'Msg) * ?int -> Async<'Reply option>
// Usage:
mailboxProcessor.PostAndTryAsyncReply (buildMessage)
mailboxProcessor.PostAndTryAsyncReply (buildMessage, timeout = timeout)
Parameters
buildMessage Type: AsyncReplyChannel<'Reply> -> 'Msg
The function to incorporate the AsyncReplyChannel into the message to be sent.
timeout Type: int
An optional timeout parameter (in milliseconds) to wait for a reply message. The default is -1 which corresponds to System.Threading.Timeout.Infinite.
Return Value
An asynchronous computation (Async object) that will return the reply or None if the timeout expires.
Example
open System
type Message = string * AsyncReplyChannel<string>
let formatString = "Message number {0} was received. Message contents: {1}"
let agent = MailboxProcessor<Message>.Start(fun inbox ->
let rec loop n =
async {
let! (message, replyChannel) = inbox.Receive();
// The delay gets longer with each message, and eventually triggers a timeout.
do! Async.Sleep(200 * n );
if (message = "Stop") then
replyChannel.Reply("Stop")
else
replyChannel.Reply(String.Format(formatString, n, message))
do! loop (n + 1)
}
loop (0))
printfn "Mailbox Processor Test"
printfn "Type some text and press Enter to submit a message."
printfn "Type 'Stop' to close the program."
let mutable isCompleted = false
while (not isCompleted) do
printf "> "
let input = Console.ReadLine()
let messageAsync = agent.PostAndTryAsyncReply((fun replyChannel -> input, replyChannel), 1000)
// Set up a continuation function (the first argument below) that prints the reply.
// The second argument is the exception continuation.
// The third argument is the cancellation continuation (not used).
Async.StartWithContinuations(messageAsync,
(fun reply ->
match reply with
| None -> printfn "Reply timeout exceeded."
| Some reply -> if (reply = "Stop") then
isCompleted <- true
else printfn "%s" reply),
(fun exn ->
printfn "Exception occurred: %s" exn.Message),
(fun _ -> ()))
printfn "Press Enter to continue."
Console.ReadLine() |> ignore
A sample session follows.
Mailbox Processor Test
Type some text and press Enter to submit a message.
Type 'Stop' to close the program.
> test1
> Message number 0 was received. Message contents: test1
test2
> Message number 1 was received. Message contents: test2
test3
> Message number 2 was received. Message contents: test3
test4
> Message number 3 was received. Message contents: test4
test5
> Message number 4 was received. Message contents: test5
test6
> Reply timeout exceeded.
Version Information
F# Core Library Versions
Supported in: 2.0, 4.0, Portable