如何从复合泛型类型中检索值？

如何从泛型中检索值？

具体来说，我正在尝试以下操作：

// Test
let result = Validate goodInput;;

// How to access record??
let request = getRequest result

这是代码：

type Result<'TSuccess,'TFailure> = 
    | Success of 'TSuccess
    | Failure of 'TFailure

let bind nextFunction lastFunctionResult = 
    match lastFunctionResult with
    | Success input -> nextFunction input
    | Failure f -> Failure f

type Request = {name:string; email:string}

let validate1 input =
   if input.name = "" then Failure "Name must not be blank"
   else Success input

let validate2 input =
   if input.name.Length > 50 then Failure "Name must not be longer than 50 chars"
   else Success input

let validate3 input =
   if input.email = "" then Failure "Email must not be blank"   
   else Success input;;

let Validate = 
    validate1 
    >> bind validate2 
    >> bind validate3;;

// Setup
let goodInput = {name="Alice"; email="[email protected] /cdn-cgi/l/email-protection"}
let badInput = {name=""; email="[email protected] /cdn-cgi/l/email-protection"};;

// I have no clue how to do this...
let getRequest = function
    | "Alice", "[email protected] /cdn-cgi/l/email-protection" -> {name="Scott"; email="[email protected] /cdn-cgi/l/email-protection"}
    | _ -> {name="none"; email="none"}

// Test
let result = Validate goodInput;;

// How to access record??
let request = getRequest result
printfn "%A" result

您的意思是如何从结果类型中提取记录？通过模式匹配，这就是您已经在做的事情bind.

let getRequest result = 
    match result with
    | Success input -> input 
    | Failure msg -> failwithf "Invalid input: %s" msg

let result = Validate goodInput
let record = getRequest result

这将返回记录或引发异常。一旦你有了自己的想法，你将如何处理成功和失败的案例Result- 这可能会引发异常，或将其转变为选项，或记录消息并返回默认值等。