MailboxProcessor.TryPostAndReply<'Msg,'Reply> 方法 (F#)
類似 MailboxProcessor.PostAndReply，但若未在逾時期限之內回覆，會傳回 None。
**命名空間/模組路徑：**Microsoft.FSharp.Control
組件：FSharp.Core (在 FSharp.Core.dll 中)
// Signature:
member this.TryPostAndReply : (AsyncReplyChannel<'Reply> -> 'Msg) * ?int -> 'Reply option
// Usage:
mailboxProcessor.TryPostAndReply (buildMessage)
mailboxProcessor.TryPostAndReply (buildMessage, timeout = timeout)
參數
buildMessage
型別：AsyncReplyChannel<'Reply> -> 'Msg用來將 AsyncReplyChannel 加入至要傳送之訊息的函式。
timeout
型別：int等待回應訊息的選擇性逾時參數 (以毫秒為單位)。 預設為 -1，對應至 Infinite。
傳回值
代理程式的回覆，如果逾時到期則為 None。
範例
下列範例顯示如何使用 TryPostAndReply。 在此範例中，代理程式的延遲最終會造成逾時。
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 will trigger 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)
let asyncReadInput =
async {
printf "> "
let input = Console.ReadLine();
return input
}
printfn "Mailbox Processor Test"
printfn "Type some text and press Enter to submit a message."
printfn "Type 'Stop' to close the program."
let rec loop() =
Async.StartWithContinuations(asyncReadInput, (fun input ->
let reply = agent.TryPostAndReply((fun replyChannel -> input, replyChannel), 1000)
match reply with
| None -> printfn "Timeout exceeded."
| Some(reply) ->
if (reply <> "Stop") then
printfn "Reply: %s" reply
loop()
else
()),
(fun exn -> ()),
(fun _ -> ()))
loop()
printfn "Press Enter to continue."
Console.ReadLine() |> ignore
範例工作階段如下。
平台
Windows 8 中， Windows 7， Windows Server 2012 上， Windows Server 2008 R2
版本資訊
F# 核心程式庫版本
支援版本:2.0， 4.0，可攜式執行檔 (PE)。