F# implementation of Facebook GraphQL query language specification.

type Person = 
    { FirstName: string
      LastName: string }

// define GraphQL type 
let PersonType = Define.Object(
    name = "Person",
    fields = [
        // property resolver will be auto-generated
        Define.AutoField("firstName", String)   
        // asynchronous explicit member resolver
        Define.AsyncField("lastName", String, resolve = fun context person -> async { return person.LastName })   
    ])
    
// include person as a root query of a schema
let schema = Schema(query = PersonType)

// retrieve person data
let johnSnow = { FirstName = "John"; LastName = "Snow" }
let reply = schema.AsyncExecute(parse "{ firstName, lastName }", johnSnow) |> Async.RunSynchronously
// #> { data: { "firstName", "John", "lastName", "Snow" } } 

It's type safe. Things like invalid fields or invalid return types will be checked at compile time.

Go to GraphiQL sample directory. In order to run it, build FSharp.Data.GraphQL project on Debug settings and run server.fsx with FSI - this will create a Suave.IO server compatible with GraphQL spec, running on port 8083. Then what you need is to run node.js graphiql frontend. To do so, run npm i to get all dependencies, and then run npm run serve | npm run dev - this will start a webpack server running on http://localhost:8090/ . Visit this link, and GraphiQL edito should appear. You may try it by applying following query:

{
  hero(id:"1000") {
    id,
    name,
    appearsIn,
    homePlanet,
    friends {
      ... on Human {
        name
      }
      ... on Droid {
        name
      }
    }
  }
}

Second sample is a F#-backed version of of popular Relay Starter Kit - an example application using React.js + Relay with Relay-compatible server API.

To run it, build a FSharp.Data.GraphQL and FSharp.Data.GraphQL.Relay projects using Debug settings. Then start server by running server.fsx script in your FSI - this will start relay-compatible F# server on port 8083. Then build node.js frontend by getting all dependencies (npm i) and running it (npm run serve | npm run dev) - this will start webpack server running React application using Relay for managing application state. You can visit it on http://localhost:8083/ .

In order to update client schema, visit http://localhost:8083/ and copy-paste the response (which is introspection query result from current F# server) into data/schema.json.