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Add Json.Encode.Extra.at counterpart to Json.Decode.at #28

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Add Json.Encode.Extra.at counterpart to Json.Decode.at #28

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28 changes: 27 additions & 1 deletion src/Json/Encode/Extra.elm
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Original file line number Diff line number Diff line change
@@ -1,4 +1,7 @@
module Json.Encode.Extra exposing (maybe)
module Json.Encode.Extra exposing
( maybe
, at
)

{-| Convenience functions for turning Elm values into Json values.

Expand All @@ -25,3 +28,26 @@ import Json.Encode exposing (Value, encode, int, null, object)
maybe : (a -> Value) -> Maybe a -> Value
maybe encoder =
Maybe.map encoder >> Maybe.withDefault null


{-| Decode a nested JSON object, requiring certain fields.

import Json.Encode exposing (..)

encodedValue : Json.Encode.Value
encodedValue =
(Json.Encode.string "Elm Street")

at [ "Nightmare", "At" ] encodedValue
|> Json.Encode.encode 0
--> "{\"Nightmare\":{\"At\":\"Elm Street\"}}"

This is really just a shorthand for:

Json.Encode.object [ ( "Nightmare", Json.Encode.object [ ( "At", encodedValue ) ] ) ]
|> Json.Encode.encode 0

-}
at : List String -> Json.Encode.Value -> Json.Encode.Value
at keys initial =
List.foldr (\k current -> Json.Encode.object [ ( k, current ) ]) initial keys