f# - 从 Suave 请求中聚合信息

Question

我正在使用 Suave 构建一个经过身份验证的 Web API，我经常偶然发现在不同功能中聚合信息的问题

pathScan Navigation.playersAvailables GetGame >>= getInSession >>= (fun (gameId,playerInSession) -> //access to both gameId and player in session)

签名:

getGame : HttpContext -> Async<HttpContext option>
getInSession : HttpContext -> Async<HttpContext option> 

getGame 从 httpContext.request.querystring 获取 id getInSession

从 httpContext.cookie 中获取 sessionId

我找到的唯一方法就是将信息存储在 userDataDictionnary 中:

Writers.setUserData "player"  { playerId= playersId; socialId=socialId; username = username}

并在另一个函数中检索它，但对我来说看起来很讨厌:

let player = x.userState.["player"] :?> PlayerSession
//do some other stuff now that we have the current player

还有另一种方法吗？我想要像这样的纯函数
getGameId 和 get Session 等，并且能够按照我希望处理不同路线的方式组合它们:

pathScan Navigation.playersAvailables GetGame >>= getInSession >>= (fun (gameId,playerInSession) -> //access to both gameId and player in session)
pathScan Navigation.otherRoute GetGame >>= (fun (gameId) -> //process gameId)
pathScan Navigation.otherRoute2 getInSession >>= (fun (sessionId) -> //process sessionId to do some other stuff)

恐怕我需要的是与一些真正的函数式程序员进行一天的交谈。

Answer 1

setUserData是纯函数 - src .

不确定是否this仍然是最新的，但它说 pathScan和 >>=不能很好地链接。不过我觉得Writers.setUserData你正在使用也许能够完成它。

使用元素袋将东西拉出来并不可爱。

怎么样:

let (|ParseInt|_|) =
    function
    | "" | null -> None
    | x ->
        match Int32.TryParse x with
        | true, i -> Some i
        | _ -> None


let (|HasParam|_|) name (ctx:HttpContext) =
    ctx.request.queryParam name
    |> function
        |Choice1Of2 value ->
            Some value
        | _ -> None

let playersAvailablePart:WebPart =
    function
    //access to both gameId and player in session
    |HasParam "inSession" playerInSession & HasParam "gameId" gameId as ctx ->
        // do your processing here, sample return:
        OK "we had all the required important parts" ctx
    // or an example of something more strongly typed
    | HasParam "inSession" (ParseInt playerInSession) & HasParam "gameId" (ParseInt gameId) as ctx ->
        // do your processing here, sample return:
        OK "we had all the required important parts" ctx
    | ctx -> never ctx

如果值不在 queryParameters 中，这并不完全有效，但您可以将其调整为它们所在的位置