F# - JSON Type Provider - Literal String

Question

I have an interesting problem using the F# Type Provider. Using the following sample json to generate the required type works beautifully but with one glaring issue - one of the values is a literal string ("235") but that string does not occur in the real data - each new record has a different three-digit number:

{
"record": {
    "235": {
        "Id": "001",
        "Name": "A. N. Other",
        "IdDatetime": "2017-11-11T13:10:00+00:00"
        ...
    }
    "255": {
        "Id": "005",
        "Name": "D. Other",
        "IdDatetime": "2017-11-11T13:10:00+00:00"
        ...
    }
}

So, unfortunately, I cannot access the Id, Name, and IdDateTime fields without knowing the three-digit code in advance!

Any advice?

Answer 1

Do you have to use the JsonProvider? There is a simpler JsonParser in FSharp.Data that allows easier access to more dynamic data. After that it's just a simple exercise to destructure it to get to the inner part.

#r @"../packages/FSharp.Data/lib/net40/FSharp.Data.dll"

open FSharp.Data
open FSharp.Data.JsonExtensions

[<Literal>]
let jsonText = """
{
"record": {
    "235": {
        "Id": "001",
        "Name": "A. N. Other",
        "IdDatetime": "2017-11-11T13:10:00+00:00"
        }
    }
}
"""

let json1 = JsonValue.Parse(jsonText)
let json2 = json1?record

let json3 = 
    match json2 with
        | JsonValue.Record x -> x

let json4 = 
    match json3 with
    [|(_,x)|] -> x

val json4 : JsonValue = { "Id": "001", "Name": "A. N. Other",
"IdDatetime": "2017-11-11T13:10:00+00:00" }

Edit

On an array of jsonvalues this works the same, except you have to map the matching function over. For example:

let jsonText2 = """
{
"record": {
    "235": {
        "Id": "001",
        "Name": "A. N. Other",
        "IdDatetime": "2017-11-11T13:10:00+00:00"
    },
    "255": {
        "Id": "005",
        "Name": "D. Other",
        "IdDatetime": "2017-11-11T13:10:00+00:00"
    }
  }
}
"""

let json1 = JsonValue.Parse(jsonText2)
let json2 = json1?record

let json3 = 
    match json2 with
        | JsonValue.Record x -> x


let json4 = 
json3 
|> Array.map (function _,x -> x) 

val json4 : JsonValue [] = [|{ "Id": "001", "Name": "A. N. Other", "IdDatetime": "2017-11-11T13:10:00+00:00" }; { "Id": "005", "Name": "D. Other", "IdDatetime": "2017-11-11T13:10:00+00:00" }|]