xerpa / elm-graphql

A fork from ghivert/elm-graphql with RemoteData support

Elm GraphQL

Opinion

Just import GraphQL, and write queries! This package suppose your decoders are already written, and do not write decoders. It only provide a nice syntax to do GraphQL queries, and decode the "data" at the root of standard GraphQL for you. Just think on your schema, and don't bother with everything else. By not writing custom decoders, you can make multiple queries on the same data, with different schemas each times. They will always be converted to the same type, avoiding you to rewrote a type for each request like others can do. Moreover, it is purely written in Elm, avoiding you to think to recompile .graphql files.

This package try to be similar to Json.Encode and Http. This allow to write things more easily if you're often involved with Elm!

How to use?

Basically, creates an object with object, add some fields with a list of field, and you're done! You can add some arguments, selectors or alias to the fields, by using the corresponding functions. Otherwise, a (huge) example:

Types.elm

module Types exposing (..)

import Json.Decode as Decode exposing (Decoder, field, maybe, int, string)
import RemoteData


type Msg
  = GraphQlMsg (RemoteData.WebData NameAndAddress)


type alias User =
  { id : Maybe Int
  , name : Maybe Name
  }


type alias Name =
  { firstName : Maybe String
  , lastName : Maybe String
  }


type alias Address =
  { street : Maybe String
  , town : Maybe String
  }

type alias NameAndAddress =
  { user : User
  , address : Address
  }

decodeName : Decoder Name
decodeName =
  Decode.map2 Name
    (maybe (field "first_name" string))
    (maybe (field "last_name" string))


decodeUser : Decoder User
decodeUser =
  Decode.map2 User
    (maybe (field "id" int))
    (maybe (field "name" decodeName))


decodeAddress : Decoder Address
decodeAddress =
  Decode.map2 Address
    (maybe (field "street" string))
    (maybe (field "town" string))


decodeNameAndAddress =
  Decode.map2 NameAndAddress
    (field "user" decodeUser)
    (field "address" decodeAddress)

Requests.elm

module Requests exposing (..)

import GraphQl
import Json.Decode as Decode exposing (Decoder, field)
import Types exposing (User, Address, Msg(..))


userRequest : GraphQl.Value Root
userRequest =
  GraphQl.object
    [ GraphQl.field "user"
      |> GraphQl.withArgument "id" (GraphQl.variable "id")
      |> GraphQl.withAlias "current_user"
      |> GraphQl.withSelectors
        [ GraphQl.field "id"
        , GraphQl.field "name"
          |> GraphQl.withSelectors
            [ GraphQl.field "first_name"
            , GraphQl.field "last_name"
            ]
        ]
    , GraphQl.field "address"
      |> GraphQl.withArgument "city" (GraphQl.string "Paris")
      |> GraphQl.withArgument "id" (GraphQl.int 12)
      |> GraphQl.withArgument "type" (GraphQl.type_ "LOFT")
      |> GraphQl.withSelectors
        [ GraphQl.field "street"
        , GraphQl.field "town"
        ]
    ]
    |> GraphQl.withVariable "id" "INT!"


baseRequest : GraphQl.Value -> Decoder a -> GraphQl.Request a
baseRequest =
  GraphQl.query "/example_endpoint"


sendRequest : Int -> Cmd Msg
sendRequest id =
  baseRequest userRequest decodeNameAndAddress
    |> GraphQl.addVariables [ ("id", Encode.int id) ]
    |> GraphQl.send
    |> Cmd.map GraphQlMsg

Licenced BSD3, enjoy the work! GraphQL is amazingly awesome!