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Accepted
Joe
Asked: 2024-08-07 21:24:05 +0800 CST

如何动态地构建镜头表现力？

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我有以下代码片段，用于读取由镜头（lens-aeson）表达式指定的值：

import           Control.Lens    ((^?))
import           Data.Aeson      (Value)
import           Data.Aeson.Key  (fromString)
import           Data.Aeson.Lens (key)
import           Data.Text       (pack)

-- >>> readValue
-- Just (String "value")
readValue :: Maybe Value
readValue = json ^? path
  where
    path = key (fromString "key") . key (fromString "of") . key (fromString "interest")
    json = pack "{\"key\": {\"of\": {\"interest\": \"value\"}}}"

现在我想通过将列表传递给来path从配置中动态构建表达式。["key","of","interest"]readValue

我如何path从列表中动态创建？

haskell

1 个回答

  1. Best Answer

    我想是这样的：

    readValue = json ^? _Value.path
  where
    path = foldr (.) id [key (fromString t) | t <- ["key", "of", "interest"]]
    json = pack "{\"key\": {\"of\": {\"interest\": \"value\"}}}"

    foldr如果您对此有强烈的感觉，您可以手动融合和列表理解。

    • 3

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