Combinator library for JSON decoding and encoding.
npm install @glennsl/rescript-json-combinators
``rescript
type point = {
x: int,
y: int,
}
type polyline = {
points: array
thickness: option
}
module Decode = {
open Json.Decode
let point = object(field => {
x: field.required(. "x", int),
y: field.required(. "y", int),
})
let polyline = object(field => {
points: field.required(. "points", array(point)),
thickness: field.optional(. "thickness", int),
})
}
let data = {
"points": [
{ "x": 1, "y": -4 },
{ "x": 5, "y": 8 }
]
}
let _ = data->Js.Json.parseExn->Json.decode(Decode.polyline)->Js.log
`
See examples for more.
`sh`
npm install --save @glennsl/rescript-json-combinators
Then add @glennsl/rescript-json-combinators to bs-dependencies in your bsconfig.json:
`diff`
{
"bs-dependencies": [
+ "@glennsl/rescript-json-combinators"
]
}
Optionally, add this to automatically open the library in order to use Json.Encode and Json.Decode directly:
`diff`
{
"bsc-flags": [
+ "-open JsonCombinators",
]
}
rescript-json-combinators is the spriritual successor of bs-json. It was rewritten from scratch and not intended to be
backwards compatible. And while for the most part is does share the same design principles,there are also some notable differences:
* Decoders have been made abstract. While the internal representation is still the same, a function that takes a Js.Json.t
and returns either the decoded value or raises an exception, they can no longer be called directly. Instead they have to be run
via . This is in order to ensure that the DecodeError exceptions don't leak and returns a result
instead. Custom decoders can still be created with .
* A new object decoder has been added, and while it's still possible to decode fields individually in a custom decoder, this
addresses a couple ergonomic problems with that approach, such as distinguishing between a field missing and having the wrong
type, and the over-use and under-encapsulation of custom decoders.
* Uncurrying and raw javascript is used in some places to improve performance. For the most part this isn't visible to the
end user because decoders can no longer be called directly. There are a couple exceptions however, such as field decoders inside
the object deocder, and map.
For the moment, please see the interface files:
* Json
* Json.Encode
* Json.Decode
This work is dual-licensed under LGPL 3.0 and
MPL 2.0. You can choose between one of them if you use this work.
Please see LICENSE.LGPL-3.0 and
LICENSE.MPL-2.0 for the full text of each license.
SPDX-License-Identifier: LGPL-3.0 OR MPL-2.0
to help with decoding recursive data structures$3
- add Decode.flatMap`