json - Elm - 如何将对象的 json 列表解码为 Dict

Question

给定对象的 JSON 列表，例如:

[{"id":"1", "name":"Jane"},{"id":"2", "name":"Joe"}]

我如何将其解码为 Dict String Foo与 id作为键和在哪里 Foo是 {id: String, name: String} 类型的记录? (请注意，该记录还包含 id。)

Answer 1

例如使用以下组合:

Json.Decode.list ( https://package.elm-lang.org/packages/elm/json/latest/Json-Decode#list

Json.Decode.map2 ( https://package.elm-lang.org/packages/elm/json/latest/Json-Decode#map2 )

Dict.fromList ( https://package.elm-lang.org/packages/elm/core/latest/Dict#fromList )

Tuple.pair ( https://package.elm-lang.org/packages/elm/core/latest/Tuple#pair )

import Dict exposing (Dict)
import Json.Decode as Decode exposing (Decoder)

type alias Foo =
    { id : String, name : String }

fooDecoder : Decoder Foo
fooDecoder =
    Decode.map2 Foo (Decode.field "id" Decode.string) (Decode.field "name" Decode.string)

theDecoder : Decoder (Dict String Foo)
theDecoder =
    Decode.list (Decode.map2 Tuple.pair (Decode.field "id" Decode.string) fooDecoder)
        |> Decode.map Dict.fromList