如何用aeson解析嵌套的JSON

本文介绍了如何用aeson解析嵌套的JSON的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 我试图用aeson解析以下表单的JSON {field：{name： ...}} 或 {tag：{name：...}} 或 {line：{number：...}} 构造以下数据类型： data规则=行整数 |字段L.ByteString |标签L.ByteString 不幸的是，我遇到了两个我没有找到解决方案的问题，即： 如何解析嵌套的JSON？查看（。：） a>，它使用查找来提取特定键的值。我很犹豫要做这样的事情，因为它似乎太依赖于aeson如何实现的具体细节。我错误地认为这是一个问题吗？ 如何根据哪个键在JSON中使用正确的数据构造函数？我所有的< |>所做的努力都让我无处可寻。 我会发布我写的代码很远，但我甚至没有到达有什么值得发布的地步。解决方案 / b> { - ＃LANGUAGE OverloadedStrings＃ - } 导入Control.Applicative 导入数据。 Aeson 导入Data.Aeson.Types 将限定的Data.ByteString导入为B 将限定的Data.ByteString.Lazy导入为L 将限定的Data.Map导入为M 数据Rule =行整数 |字段L.ByteString |标签L.ByteString 派生显示 实例FromJSON规则其中 parseJSON j = do o 案例M.toList（o :: Object） [（field，Object o'）] - >字段< $> o'。：name [（tag，Object o'）] - >标签< $> o'。：name [（line，Object o'）] - >行< $> o'。：number _ - >失败规则：意外格式 I am trying to parse JSON of the following form using aeson{"field":{"name":"..."}}or{"tag":{"name":"..."}}or{"line":{"number":"..."}}to construct the following data typedata Rule = Line Integer | Field L.ByteString | Tag L.ByteStringUnfortunately, I face two problems that I've not found solutions to, namely:How do I parse nested JSON? Looking at the implementation of (.:), it uses lookup to extract a specific key's value. I'm hesitant to do something like this as it seems to be relying too much on the specifics of how aeson implements things. Am I wrong in thinking this is an issue?How do I use the correct data constructor based on which key is present in the JSON? All my efforts with <|> have led me nowhere.I would post the code I've written thus far, but I haven't even gotten to the point where I have anything worth posting. 解决方案 How about the following?{-# LANGUAGE OverloadedStrings #-}import Control.Applicativeimport Data.Aesonimport Data.Aeson.Typesimport qualified Data.ByteString as Bimport qualified Data.ByteString.Lazy as Limport qualified Data.Map as Mdata Rule = Line Integer | Field L.ByteString | Tag L.ByteString deriving Showinstance FromJSON Rule where parseJSON j = do o <- parseJSON j -- takes care of JSON type check case M.toList (o :: Object) of [("field", Object o')] -> Field <$> o' .: "name" [("tag", Object o')] -> Tag <$> o' .: "name" [("line", Object o')] -> Line <$> o' .: "number" _ -> fail "Rule: unexpected format" 这篇关于如何用aeson解析嵌套的JSON的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！