Data.Aeson.Picker

Documentation

(|--) :: (AsValue t, FromJSON a) => t -> [Text] -> a infix 5

From given JSON and selectors returns typed field. If input JSON is not valid or selected field is not found then error is thrown. If you need more safe way use '(|-?)' instead. Examples:

ghci> "5" |-- [] :: Int
5
ghci> "5" |-- [] :: Float
5.0
ghci>"5" |-- [] :: String
*** Exception: Data.Aeson.Picker: could not pick field with path: []

ghci> :set -XOverloadedStrings
ghci> "{\"a\": 5}" |-- ["a"] :: Int
5
ghci> "{\"a\": 5}" |-- ["b"] :: Int
*** Exception: Data.Aeson.Picker: could not pick field with path: ["b"]
ghci> "{\"outer\": {\"inner\": [1,2,3]}}" |-- ["outer", "inner"] :: [Int]
[1,2,3]
ghci> {\"outer\": {\"inner\": [1,2,3]}}" |-- ["outer", "inner"] :: [Double]
[1.0,2.0,3.0]
ghci> "{a: 5}" |-- ["a"] :: Int
*** Exception: Data.Aeson.Picker: input json is not valid

(|-?) :: (AsValue t, FromJSON a) => t -> [Text] -> Maybe a infix 5

From given JSON and selectors returns typed field inside Maybe. If input JSON is not valid then error is thrown. Examples:

ghci> "5" |-? [] :: Maybe Int
Just 5
ghci> "5" |-? [] :: Maybe String
Nothing
ghci> "{\"a\": 5}" |-? ["a"] :: Maybe Int
Just 5
ghci> "{a: 5}" |-? ["a"] :: Maybe Int
*** Exception: Data.Aeson.Picker: input json is not valid