pimbrouwers/jay

An F# JSON parser & serializer

Jay

The aim of this library was to take the core JSON parser from the amazing FSharp.Data project, and modernize/simplify it's API.

Getting Started

Install the Jay NuGet package:

PM>  Install-Package Jay

Or using the dotnet CLI

dotnet add package Jay

An Example

Let's consider a stripped down Tweet object.

Note: the user and entities properties have been removed for clarity.

{
 "created_at": "Wed Oct 10 20:19:24 +0000 2018",
 "id": 1050118621198921728,
 "id_str": "1050118621198921728",
 "text": "To make room for more expression, we will now count all emojis as equal—including those with gender‍‍‍ ‍‍and skin t… https://t.co/MkGjXf9aXm", 
}

In order to work with this in our F# program, we'll first need to create a record type.

type Tweet = 
    {
        CreatedAt : DateTimeOffset
        Id        : int64
        IdStr     : string
        Text      : string
    }

Next we'll define a module with the same name, Tweet, and a function called fromJson to consume our JSON and return a Tweet record.

type Tweet = 
    {
        CreatedAt : DateTimeOffset
        Id        : int64
        IdStr     : string
        Text      : string
    }

module Tweet =
    let fromJson (json : Json) =
        {
            CreatedAt = json?created_at.AsDateTimeOffset()
            Id        = json?id.AsInt64()
            IdStr     = json?idStr.AsString()
            Text      = json?text.AsString()
        }


let tweetJson = ... // JSON from above
let tweet = 
    tweetJson
    |> Json.parse
    |> Tweet.fromJson

Finally, we'll create another function toJson to convert our record back into JSON represented as an abstract syntax tree.

type Tweet = 
    {
        CreatedAt : DateTimeOffset
        Id        : int64
        IdStr     : string
        Text      : string
    }

module Tweet =
    let fromJson (json : Json) =
        {
            CreatedAt = json?created_at.AsDateTimeOffset()
            Id        = json?id.AsInt64()
            IdStr     = json?idStr.AsString()
            Text      = json?text.AsString()
        }

    let toJson (tweet : Tweet) =
        JObject 
            [|
                "created_at", JString (tweet.CreatedAt.ToString())
                "id",         JNumber (float tweet.Id)
                "id_str",     JString tweet.IdStr
                "text",       JString tweet.Text
            |]

let tweetJson = ... // JSON from above
let tweet = 
    tweetJson
    |> Json.parse
    |> Tweet.fromJson

let json =
    tweet
    |> Tweet.toJson
    |> Json.serialize

And that's it!

Find a bug?

There's an issue for that.

License

Built with ♥ by Pim Brouwers in Toronto, ON. Licensed under Apache License 2.0.

jay's Issues

Performance comparison

How does the performance compare to other JSON serializers available in F#?

Reading Json that contains comments

Hi,

It looks to me like Jay doesn't like parsing Json that contains comments...
Those might not be 'officially' supported, but I see that FSharp.Data was changed to ignore them rather than breaking in fsprojects/FSharp.Data#1448, so would there be any interest in trying to port that change over to here?