x : { v : Float, pos : Float } , y : { v : ...

Question

You can create tuples pretty much the same way you create records like

just by replacing the record constructor with the pair construction function

:

type alias Properties a =
    { a
        | x : { v : Float, pos : Float }
        , y : { v : Float, pos : Float }
        , size : ( Float, Float )
        , el : Float
    }

type alias Pr =
    { v : Float, pos : Float }

type Block
    = Block BlockType BlockProp


type alias BlockProp =
    Properties { visibility : Int, tb : ( Float, Float ) }


type BlockType
    = Rock
    | Ground

Similarly, to get the block type you need to decode

{
    "blocks": [{
            "type": "ground",
            "x": {
                "v": "0.0",
                "pos": "30"
            },
            "y": {
                "v": "0.0",
                "pos": "100.0"
            },
            "sizex": "50.0",
            "sizey": "70.0",
            "el": "1.0",
            "visibility": "1",
            "t": "20.0",
            "b": "30.0"
        },
        {
            "type": "rock",
            "x": {
                "v": "0.0",
                "pos": "30"
            },
            "y": {
                "v": "0.0",
                "pos": "100.0"
            },
            "sizex": "50.0",
            "sizey": "70.0",
            "el": "1.0",
            "visibility": "1",
            "t": "20.0",
            "b": "30.0"
        }
    ]
}

as a type Block, then map the result of that using a function that converts

s to

blockDecoder : Decoder BlockProp
blockDecoder =
    map6 BlockProp
        (field "x"
            (map2 Pr
                (field "v" float)
                (field "pos" float)
            )
        )
        (field "y"
            (map2 Pr
                (field "v" float)
                (field "pos" float)
            )
        )
        (field "size" -- I DON'T KNOW HOW TO CONVERT sizex AND sizey TO TUPLE
        (field "el" float)
        (field "visibility" float)
        (field "tb" -- I DON'T KNOW HOW TO CONVERT t AND b TO TUPLE

s:

Answer 1

而我需要对保存在JSON中的块进行解码。Pr有谁能帮我解决如何构建一个解码器 把保存在JSON中的区块转换为： Tuple.pair? :)

map2 Tuple.pair
    (field "sizex" float)
    (field "sizey" float)

edit:我试过这样的东西。type我在将字段转换为元组时遇到了问题... ... 同时我也不知道如何根据类型字段创建一个具有正确BlockType的Block。String String BlockType我目前正在学习Elm，我被卡在了JSON的解码上。我有一个代表块的结构：类型别名 属性a = { a