如何使用镜头在Aeson.Object中的所有键/值对上进行concatMap

问题描述

我一直在愚弄Control.Lens.Indexed中的组合器，尤其是 iconcatMap ，但是我无法使用 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 iconcatMapOf .另外，请注意， members 会使用 AsValue 实例遍历类型，并且 Object 没有此类实例，因此我们需要将其包装到值.

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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