[英]Elm: Decoding a nested array of objects with elm-decode-pipeline
I am struggling to convert a JSON response from OpenWeatherMap using NoRedInk/elm-decode-pipeline.我正在努力使用 NoRedInk/elm-decode-pipeline 转换来自 OpenWeatherMap 的 JSON 响应。 I have managed to decode nested objects within the JSON, but I cannot do the same for an array of objects我已经设法解码 JSON 中的嵌套对象,但我不能对对象数组做同样的事情
I've included the code I currently have.我已经包含了我目前拥有的代码。 It compiles but in fails when run with FetchWeather Err BadPayload ...
它编译但在使用FetchWeather Err BadPayload ...
JSON JSON
{
"weather":[{"id":804}],
"main":{"temp":289.5},
}
CODE代码
type alias OpenWeatherResponse =
{ main: MainResult
, weather: WeatherResult
}
type alias MainResult =
{ temp: Float }
type alias ConditionResult =
{ code: Int }
decodeOpenWeatherResponse : Decoder OpenWeatherResponse
decodeOpenWeatherResponse =
decode OpenWeatherResponse
|> required "main" decodeMain
|> required "weather" decodeConditions
decodeMain : Decoder MainResult
decodeMain =
decode MainResult
|> required "temp" float
decodeConditions : Decoder ConditionResult
decodeConditions =
decode ConditionResult
|> required "id" int -- This is clearly wrong --
You can use Json.Decode.list : Decoder a -> Decoder (List a)
to make a parser of a list from a parser of an item.您可以使用Json.Decode.list : Decoder a -> Decoder (List a)
从项目的解析器中生成列表的解析器。
decodeConditions : Decoder (List ConditionResult)
decodeConditions =
Json.Decode.list decodeCondition
decodeCondition : Decoder ConditionResult
decodeCondition =
decode ConditionResult
|> required "id" int
Or, you can make it look like a part of the pipeline:或者,您可以让它看起来像管道的一部分:
decodeConditions : Decoder (List ConditionResult)
decodeConditions=
decode ConditionResult
|> required "id" int
|> Json.Decode.list
Also, the response type has to have a list:此外,响应类型必须有一个列表:
type alias OpenWeatherResponse =
{ main : MainResult
, weather : List ConditionResult
}
If you just want the first item of the weather
array, you can use Json.Decode.index : Int -> Decoder a -> Decoder a
:如果你只想要weather
数组的第一项,你可以使用Json.Decode.index : Int -> Decoder a -> Decoder a
:
decodeConditions : Decoder ConditionResult
decodeConditions =
decode ConditionResult
|> required "id" int
|> Json.Decode.index 0
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