如何使用镜头在Aeson.Object中的所有键/值对上进行concatMap [英] How to concatMap over all key/value pairs in an Aeson.Object using lenses

问题描述

我一直在愚弄Control.Lens.Indexed中的组合器，尤其是 数据.Aeson.Lens.members 镜头:

I've been fooling around with the combinators in Control.Lens.Indexed, especially iconcatMap, but I haven't been able to come-up with a function with the following type-sig using the Data.Aeson.Lens.members lens:

func 

  -- list of key/value pairs, essentially
  :: Aeson.Object                  

  -- function for the concatMap operation to which the 
  -- key (Text) and value is passed
  -> (Text -> Aeson.Value -> [a])  

  -- resultant concatenated list
  -> [a]

推荐答案

所需的功能是

The desired function is iconcatMapOf. Also, note that members traverses types with AsValue instance, and there's no such instance for Object, so we need to wrap it to Value.

import qualified Data.Aeson as Aeson
import Control.Lens
import Data.Aeson.Lens
import Data.Text

func :: Aeson.Object -> (Text -> Aeson.Value -> [a]) -> [a]
func obj f = iconcatMapOf members f (Aeson.Object obj)

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