F＃中的静态成员赋值和JSON解析

Question

Is JSON parsing possible into a type data or any other form where I can access each individual item within F# using built-in Microsoft provided library?

Following is an output generated by the following code.

"{"account_type":"type1","address":"US","preferred_languages":["en","ar","cn"],"displayName":"John","last_name":"Doe"}"

type Token = {access_token: string; refresh_token: string}

type Authentication =
    new() = {}
    static member token = null;

member this.RequestToken(credentials) =
    let url = "example.com"
    let request = WebRequest.Create(url) :?> HttpWebRequest
    request.Method <- "POST"
    request.ContentLength <- (int64)data.Length

    use requestStream = request.GetRequestStream() 
    requestStream.Write(data, 0, (data.Length))
    requestStream.Flush()
    requestStream.Close()

    let response = request.GetResponse() :?> HttpWebResponse

    use reader = new StreamReader(response.GetResponseStream())
    let output = reader.ReadToEnd()

    reader.Close()
    response.Close()
    request.Abort()

    Authentication.token = JsonConvert.DeserializeObject<Token>(output)
    // the value or constructor "Token" is not defined

Preferably in a type, for instance

type Token = {access_token: string; refresh_token: string}

Edit

Attempting using JSON.net

Answer 1

You will need to use an external library of some kind. If you want to get the most out of F#, you can solve this very nicely using the F# Data JSON type provider .

The type provider can infer type of JSON data from a sample, so you could parse the above data by using your sample response to guide the inference and then use the inferred type to parse more data:

open FSharp.Data

// Define a type using a sample JSON
type Account = JsonProvider<"""
  { "account_type":"type1","address":"US",
    "preferred_languages":["en","ar","cn"],
    "displayName":"John","last_name":"Doe"}""">

// Now, parse actual data you loaded from somewhere
let parsed = Account.Parse(data)

// Access all the members using a member generated by the type provider.
parsed.AccountType
parsed.Address
parsed.PreferredLanguages |> Seq.length