Control.MailboxProcessor<'Msg> 類別 (F#)

發行項
08/12/2011

更新：2010 年 8 月

可執行非同步計算的訊息處理代理程式。

命名空間/模組路徑：Microsoft.FSharp.Control

組件：FSharp.Core (在 FSharp.Core.dll 中)

[<Sealed>]
[<AutoSerializable(false)>]
type MailboxProcessor<'Msg> =
 class
  interface IDisposable
  new MailboxProcessor : (MailboxProcessor<'Msg> -> Async<unit>) * ?CancellationToken -> MailboxProcessor<'Msg>
  member this.Post : 'Msg -> unit
  member this.PostAndAsyncReply : (AsyncReplyChannel<'Reply> -> 'Msg) * int option -> Async<'Reply>
  member this.PostAndReply : (AsyncReplyChannel<'Reply> -> 'Msg) * int option -> 'Reply
  member this.PostAndTryAsyncReply : (AsyncReplyChannel<'Reply> -> 'Msg) * ?int -> Async<'Reply option>
  member this.Receive : ?int -> Async<'Msg>
  member this.Scan : ('Msg -> Async<'T> option) * ?int -> Async<'T>
  member this.Start : unit -> unit
  static member Start : (MailboxProcessor<'Msg> -> Async<unit>) * ?CancellationToken -> MailboxProcessor<'Msg>
  member this.TryPostAndReply : (AsyncReplyChannel<'Reply> -> 'Msg) * ?int -> 'Reply option
  member this.TryReceive : ?int -> Async<'Msg option>
  member this.TryScan : ('Msg -> Async<'T> option) * ?int -> Async<'T option>
  member this.add_Error : Handler<Exception> -> unit
  member this.CurrentQueueLength :  int
  member this.DefaultTimeout :  int with get, set
  member this.Error :  IEvent<Exception>
  member this.remove_Error : Handler<Exception> -> unit
 end

備註

此代理程式會封裝可支援多重寫入器和單一讀取器代理程式的訊息佇列。寫入器會使用 Post 方法與其變數，傳送訊息給代理程式。此代理程式可以使用 Receive 或 TryReceive 方法等待訊息，或是使用 Scan 或 TryScan 方法掃描所有的可用訊息。

這個型別在 .NET 組件中名為 FSharpMailboxProcessor。如果是透過 F# 以外的 .NET 語言存取型別，或透過反映存取型別，請使用這個名稱。

建構函式

成員	說明
new	建立代理程式。 body 函式會用來產生由代理程式執行的非同步計算。在呼叫 Start 之前不會執行這個函式。

執行個體成員

成員	說明
add_Error	執行代理程式而造成例外狀況時發生。
CurrentQueueLength	傳回代理程式之訊息佇列中的未處理訊息數目。
DefaultTimeout	如果未在此時間內收到訊息，則會引發逾時例外狀況。預設不會使用逾時。
錯誤	執行代理程式而造成例外狀況時發生。
Post	非同步將訊息發佈至 MailboxProcessor 的訊息佇列。
PostAndAsyncReply	非同步將訊息發佈至代理程式，並在通道上等待回覆。
PostAndReply	同步將訊息發佈至代理程式，並在通道上等待回覆。
PostAndTryAsyncReply	與 AsyncPostAndReply 類似，但會在未於逾時期間內回覆時傳回 None。
Receive	等待訊息。這將會使用第一個收到的訊息。
remove_Error	執行代理程式而造成例外狀況時發生。
Scan	在多個訊息內依照收到的順序掃描訊息，直到 scanner 傳回 Some 這個值為止。其他訊息仍在佇列中。
啟動	啟動代理程式。
TryPostAndReply	與 PostAndReply 類似，但會在未於逾時期間內回覆時傳回 None。
TryReceive	等待訊息。這將會使用第一個收到的訊息。
TryScan	在多個訊息內依照收到的順序掃描訊息，直到 scanner 傳回 Some 這個值為止。其他訊息仍在佇列中。

靜態成員

成員	說明
啟動	建立並啟動代理程式。 body 函式會用來產生由代理程式執行的非同步計算。

範例

下列範例將示範基本使用 MailboxProcessor類別。

open System
open Microsoft.FSharp.Control

type Message(id, contents) =
    static let mutable count = 0
    member this.ID = id
    member this.Contents = contents
    static member CreateMessage(contents) =
        count <- count + 1
        Message(count, contents)

let mailbox = new MailboxProcessor<Message>(fun inbox ->
    let rec loop count =
        async { printfn "Message count = %d. Waiting for next message." count
                let! msg = inbox.Receive()
                printfn "Message received. ID: %d Contents: %s" msg.ID msg.Contents
                return! loop( count + 1) }
    loop 0)

mailbox.Start()

mailbox.Post(Message.CreateMessage("ABC"))
mailbox.Post(Message.CreateMessage("XYZ"))


Console.WriteLine("Press any key...")
Console.ReadLine() |> ignore

範例輸出

下列範例顯示如何使用 MailboxProcessor來建立一個簡單的代理程式，接受各種類型的訊息，並傳回適當的回覆。此伺服器代理程式代表是購買和銷售的代理程式，在股票交換，設定叫牌，並要求資產的價格在市場製造者。用戶端可以查詢價格，或購買與出售股份。

open System

type AssetCode = string

type Asset(code, bid, ask, initialQuantity) =
    let mutable quantity = initialQuantity
    member this.AssetCode = code
    member this.Bid = bid
    member this.Ask = ask
    member this.Quantity with get() = quantity and set(value) = quantity <- value


type OrderType =
    | Buy of AssetCode * int
    | Sell of AssetCode * int

type Message =
    | Query of AssetCode * AsyncReplyChannel<Reply>
    | Order of OrderType * AsyncReplyChannel<Reply>
and Reply =
    | Failure of string
    | Info of Asset
    | Notify of OrderType

let assets = [| new Asset("AAA", 10.0, 10.05, 1000000);
                new Asset("BBB", 20.0, 20.10, 1000000);
                new Asset("CCC", 30.0, 30.15, 1000000) |]

let codeAssetMap = assets
                   |> Array.map (fun asset -> (asset.AssetCode, asset))
                   |> Map.ofArray

let mutable totalCash = 00.00
let minCash = -1000000000.0
let maxTransaction = 1000000.0

let marketMaker = new MailboxProcessor<Message>(fun inbox ->
    let rec Loop() =
        async {
            let! message = inbox.Receive()
            match message with
            | Query(assetCode, replyChannel) ->
                match (Map.tryFind assetCode codeAssetMap) with
                | Some asset ->
                    printfn "Replying with Info for %s" (asset.AssetCode)
                    replyChannel.Reply(Info(asset))
                | None -> replyChannel.Reply(Failure("Asset code not found."))
            | Order(order, replyChannel) ->
                match order with
                | Buy(assetCode, quantity) ->
                    match (Map.tryFind assetCode codeAssetMap) with
                    | Some asset ->
                        if (quantity < asset.Quantity) then
                            asset.Quantity <- asset.Quantity - quantity
                            totalCash <- totalCash + float quantity * asset.Ask
                            printfn "Replying with Notification:\nBought %d units of %s at price $%f. Total purchase $%f."
                                    quantity asset.AssetCode asset.Ask (asset.Ask * float quantity)
                            printfn "Marketmaker balance: $%10.2f" totalCash
                            replyChannel.Reply(Notify(Buy(asset.AssetCode, quantity)))
                        else
                            printfn "Insufficient shares to fulfill order for %d units of %s."
                                    quantity asset.AssetCode
                            replyChannel.Reply(Failure("Insufficient shares to fulfill order."))
                    | None -> replyChannel.Reply(Failure("Asset code not found."))
                | Sell(assetCode, quantity) ->
                    match (Map.tryFind assetCode codeAssetMap) with
                    | Some asset ->
                        if (float quantity * asset.Bid <= maxTransaction && totalCash - float quantity * asset.Bid > minCash) then
                            asset.Quantity <- asset.Quantity + quantity
                            totalCash <- totalCash - float quantity * asset.Bid
                            printfn "Replying with Notification:\nSold %d units of %s at price $%f. Total sale $%f."
                                    quantity asset.AssetCode asset.Bid (asset.Bid * float quantity)
                            printfn "Marketmaker balance: $%10.2f" totalCash
                            replyChannel.Reply(Notify(Sell(asset.AssetCode, quantity)))
                        else
                            printfn "Insufficient cash to fulfill order for %d units of %s."
                                    quantity asset.AssetCode
                            replyChannel.Reply(Failure("Insufficient cash to cover order."))
                    | None -> replyChannel.Reply(Failure("Asset code not found."))
            do! Loop()
        }
    Loop())

marketMaker.Start()

// Query price.
let reply1 = marketMaker.PostAndReply(fun replyChannel -> 
    printfn "Posting message for AAA"
    Query("AAA", replyChannel))

// Test Buy Order.
let reply2 = marketMaker.PostAndReply(fun replyChannel -> 
    printfn "Posting message for BBB"
    Order(Buy("BBB", 100), replyChannel))

// Test Sell Order.
let reply3 = marketMaker.PostAndReply(fun replyChannel -> 
    printfn "Posting message for CCC"
    Order(Sell("CCC", 100), replyChannel))

// Test incorrect code.
let reply4 = marketMaker.PostAndReply(fun replyChannel -> 
    printfn "Posting message for WrongCode"
    Order(Buy("WrongCode", 100), replyChannel))

// Test too large a number of shares.

let reply5 = marketMaker.PostAndReply(fun replyChannel ->
    printfn "Posting message with large number of shares of AAA."
    Order(Buy("AAA", 1000000000), replyChannel))

// Too large an amount of money for one transaction.

let reply6 = marketMaker.PostAndReply(fun replyChannel ->
    printfn "Posting message with too large of a monetary amount."
    Order(Sell("AAA", 100000000), replyChannel))

let random = new Random()
let nextTransaction() =
    let buyOrSell = random.Next(2)
    let asset = assets.[random.Next(3)]
    let quantity = Array.init 3 (fun _ -> random.Next(1000)) |> Array.sum
    match buyOrSell with
    | n when n % 2 = 0 -> Buy(asset.AssetCode, quantity)
    | _ -> Sell(asset.AssetCode, quantity)

let simulateOne() =
   async {
       let! reply = marketMaker.PostAndAsyncReply(fun replyChannel ->
           let transaction = nextTransaction()
           match transaction with
           | Buy(assetCode, quantity) -> printfn "Posting BUY %s %d." assetCode quantity
           | Sell(assetCode, quantity) -> printfn "Posting SELL %s %d." assetCode quantity
           Order(transaction, replyChannel))
       printfn "%s" (reply.ToString())
    }

let simulate =
    async {
        while (true) do
            do! simulateOne()
            // Insert a delay so that you can see the results more easily.
            do! Async.Sleep(1000)
    }

Async.Start(simulate)

Console.WriteLine("Press any key...")
Console.ReadLine() |> ignore

範例輸出

平台

Windows 7、Windows Vista SP2、Windows XP SP3、Windows XP x64 SP2、Windows Server 2008 R2、Windows Server 2008 SP2、Windows Server 2003 SP2

版本資訊

F# 執行階段

支援版本：2.0、4.0

Silverlight

支援版本：3

請參閱

參考

Microsoft.FSharp.Control 命名空間 (F#)

變更記錄

日期	History	原因
2010 年 8 月	加入程式碼範例。	資訊加強。

2010 年 8 月

加入程式碼範例。

資訊加強。

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