使用 ppx_yojson_conv 反序列化 JSON 資料

任務

資料格式 / JSON / 反序列化 JSON 資料

使用的 Opam 套件

• ppx_yojson_conv 測試版本: v0.17.0 — 使用的函式庫: ppx_yojson_conv
• yojson 測試版本: 2.1.2 — 使用的函式庫: yojson

程式碼

(* We open `Ppx_yojson_conv_lib.Yojson_conv.Primitives` to bring the functions that deserialise primitive types in scope. *) open Ppx_yojson_conv_lib.Yojson_conv.Primitives let json = {| { "name": "ocaml", "url": "https://ocaml.dev.org.tw/" } |} (* The annotation `[@@deriving of_yojson]` causes the PPX from `ppx_yojson_conv` to generate a function `language_of_yojson` that converts values from type `Yojson.Safe.t` to `language`. *) type language = { name: string; url: string } [@@deriving of_yojson] (* First we convert the JSON string to `Yojson.Safe.t` and then we use the generated function to create the record. If parsing fails, an `Of_yojson_error` exception is thrown that we can handle. *) try let result = json |> Yojson.Safe.from_string |> language_of_yojson Some result with Ppx_yojson_conv_lib.Yojson_conv.Of_yojson_error (exception, _) -> let _ = Printexc.to_string exception print_endline in None

open Ppx_yojson_conv_lib.Yojson_conv.Primitives

let json = {|
{
  "name": "ocaml",
  "url": "https://ocaml.dev.org.tw/"
}
|}

type language = { 
  name: string; 
  url: string 
} [@@deriving of_yojson]

try
  let result = 
    json
    |> Yojson.Safe.from_string 
    |> language_of_yojson 
  Some result
with Ppx_yojson_conv_lib.Yojson_conv.Of_yojson_error (exception, _) ->
  let _ = 
    Printexc.to_string exception print_endline in
  None

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