Is there a "functional" API for JSON?

[njlr]

It seems that the JSON functionality is implemented as member functions (e.g. json.GetProperty("foo")).

However, I would like to have a module of functions that I can use in a more "functional" style.

Does this exist in FSharp.Data?

[panesofglass]

You can get the JsonValue and manipulate the AST directly: http://fsharp.github.io/FSharp.Data/library/JsonValue.html and http://fsharp.github.io/FSharp.Data/reference/fsharp-data-jsonvalue.html

[github-actions]

🤖 This is an automated response from Repo Assist.

Yes, FSharp.Data does support functional-style JSON manipulation! There are two main approaches:

1. JsonValue AST (functional, pattern matching)

JsonValue is a discriminated union you can pattern-match over:

open FSharp.Data

let json = JsonValue.Parse """{"name": "Alice", "age": 30}"""

// Pattern matching
match json with
| JsonValue.Record props ->
    props |> Array.iter (fun (key, value) -> printfn "%s = %A" key value)
| _ -> ()

// Functional traversal
let name = json.["name"].AsString()
let age  = json.["age"].AsInteger()

2. JsonExtensions operators

The FSharp.Data.JsonExtensions module provides operators for concise functional access:

open FSharp.Data
open FSharp.Data.JsonExtensions

let json = JsonValue.Parse """{"user": {"name": "Alice"}}"""

// The ? operator for property access
let name = json?user?name.AsString()

// Iteration
for prop in json.Properties() do
    printfn "%s: %A" (fst prop) (snd prop)

3. Combinators on JsonValue

JsonValue has many functional-style methods: .Properties(), .AsArray(), .TryGetProperty(name), .AsString(), .AsInteger(), etc.

The JsonProvider type provider generates strongly-typed wrappers on top of these, but you can always drop down to JsonValue when you want more flexibility.

Is there a specific use case you had in mind? If you're processing arbitrarily-shaped JSON without a fixed schema, the JsonValue approach is usually the right fit.

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[dsyme]

Good answer 👍