[英]Decoding nested JSON structures
我正在嘗試使用elmplayground的源代碼,並且正在嘗試為博客創建配置json文件。 我現在遇到的問題是,我不知道如何將帖子/頁面作者解碼為嵌套結構。 我想要的是帖子和頁面中的author
字段在config.json
引用了一個作者。
config.json:
{
"posts": [{
"slug": "/hello-world",
"title": "Hello World",
"name": "hello-world",
"publishedDate": "2016-10-30",
"author": "Gabriel",
"intro": ""
}],
"pages": [{
"slug": "/hello",
"name": "index",
"title": "Elm Playground",
"publishedDate": "2016-09-01",
"author": "Gabriel",
"intro": ""
}],
"authors": {
"Gabriel": {
"name": "Gabriel Perales",
"avatar": "..."
}
}
}
鍵入頁面和帖子的內容:
type alias Content =
{ title : String
, name : String
, slug : String
, publishedDate : Date
, author : Author
, markdown : WebData String
, contentType : ContentType
, intro : String
}
類型作者:
type alias Author =
{ name : String
, avatar : String
}
當前,這是我的配置解碼器:
configDecoder : Decoder Config
configDecoder =
Decode.map2 Config
(field "posts" <| Decode.list <| decodeContent Post)
(field "pages" <| Decode.list <| decodeContent Page)
decodeContent : ContentType -> Decoder Content
decodeContent contentType =
Decode.map8 Content
(field "slug" string)
(field "name" string)
(field "title" string)
(field "publishedDate" decodeDate)
(field "author"
(string
-- I want to decode the author from "authors"
-- I have tried with
-- (\name -> at ["authors", name] decodeCofigAuthor) but it doesn\'t work
|> andThen (\name -> Decode.succeed <| Author name "...")
)
)
(Decode.succeed RemoteData.NotAsked)
(Decode.succeed contentType)
(field "intro" string)
decodeConfigAuthor : Decoder Author
decodeConfigAuthor =
Decode.map2 Author
(field "name" string)
(field "avatar" string)
我將從解碼作者開始,然后使用andThen
將作者Dict
傳遞給decodeContent
。 然后,您可以使用Decode.map
將作者姓名轉換為authors
Dict
的查找內容。
decoder =
(field "authors" <| Decode.dict <| authorDecoder)
|> Decode.andThen configDecoder
configDecoder authors =
Decode.map2 Config
(field "posts" <| Decode.list <| decodeContent Post authors)
(field "pages" <| Decode.list <| decodeContent Page authors)
decodeContent contentType authors =
Decode.map8 Content
-- …
(field "author" (string |> Decode.map (\name -> Dict.get name authors)))
-- …
這會改變你的模型使用Maybe Author
,但你也可以使用Decode.andThen
並返回Decode.fail
如果Dict.get
返回Nothing
。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.