FSharp - 基于数组匹配和返回记录的意外行为

Question

我刚刚进入FSharp并且我一直在努力解决这个问题很长一段时间因为我无法理解为什么我没有在比赛声明中得到我预期的结果.

根据消息号,我需要将数组中的某些值(拆分)与我想要返回的记录上的字段相匹配.

let UNMATCHED = "UNMATCHED"
let T0200 = "T0200" ;; let R0200 = "R0200"

let matchTypes = [| { MessageType = T0200; Regex = REGEX_T0200 }
                ; { MessageType = R0200; Regex = REGEX_R0200 }
...

let messageInfo (matchType:MatchType, line:string) =
    let matching = Regex.Match(line, REGEX_DATA)
    let splits = matching.Value.Replace("[","").Replace("]","").Split('|')
    let showSplit (x:string[]) = "[" + String.Join(";",x) + "]"
    let info =
        Console.WriteLine("matching against: " + matchType.MessageType)
        match matchType.MessageType with
            | T0200 -> 
                { MessageType = T0200; CustomerID = splits.[1]; CustomerName = "";
                        ItemID = splits.[2]; ItemDescription = "" }
            | R0200 ->
                { MessageType = R0200; CustomerID = splits.[1]; CustomerName = splits.[2];
                        ItemID = splits.[5]; ItemDescription = splits.[6] }
            ...
            | UNMATCHED ->  { MessageType = UNMATCHED; CustomerID = ""; CustomerName = "";
                        ItemID = ""; ItemDescription = "" }
            | _ ->  { MessageType = UNMATCHED; CustomerID = ""; CustomerName = "";
                        ItemID = ""; ItemDescription = "" }
    Console.WriteLine("messageInfo: {0}", (matchType, showSplit splits, info))
    info

但是,这似乎不起作用,从下面的输出中,我得到了T0200的预期结果,但是对于R0200,字段的映射与数组中的字段不匹配 - 即.它似乎使用与T0200语句相同的数组索引.我对所有其他后续消息都有完全相同的问题.

matching against: T0200
messageInfo: ({MessageType = "T0200";
 Regex = "\sT0200\[([\w\s]*\|)*[\w\s]*\]";}, [3;000008757051;1401], {MessageType = "T0200";
 CustomerID = "000008757051";
 CustomerName = "";
 ItemID = "1401";
 ItemDescription = "";})
matching against: R0200
messageInfo: ({MessageType = "R0200";
 Regex = "\sR0200\[([\w\s]*\|)*[\w\s]*\]";}, [3;000008757051;Ricky Bobby;413792;0;1401;SNACKER;909;0], {MessageType = "R0200";
 CustomerID = "000008757051";
 CustomerName = "";
 ItemID = "Ricky Bobby";
 ItemDescription = "";})

我猜我的匹配声明中的语法有问题 - 我做错了什么？

我在ubuntu上运行dotnet core 2.0.2

谢谢

Answer 1

MessageType是一个字符串,T0200只是一个命名的字符串值.当你尝试匹配时,T0200它实际上将字符串绑定到,T0200并始终进入你的第一个分支match.模式匹配语言不允许您匹配类似的值名称.您可以匹配有区别的联合案例,文字值和一些其他事物.看到这里.