VtUtils.JSON

JSON utilities

Example of the data type, that supports JSON encoding and decoding with Aeson:

  data Foo = Foo
      { foo :: Int
      , bar :: Text
      } deriving Generic
  instance FromJSON Foo
  instance ToJSON Foo

Documentation

data JSONDecodeFileException

Exception for jsonDecodeFile function

Constructors

JSONDecodeFileException

Fields

• filePath :: Text

  Specified file path

• message :: Text

  Decoding error

Instances

Show JSONDecodeFileException

Defined in VtUtils.JSON

Methods

showsPrec :: Int -> JSONDecodeFileException -> ShowS

show :: JSONDecodeFileException -> String

showList :: [JSONDecodeFileException] -> ShowS

Exception JSONDecodeFileException

Defined in VtUtils.JSON

Methods

toException :: JSONDecodeFileException -> SomeException

fromException :: SomeException -> Maybe JSONDecodeFileException

displayException :: JSONDecodeFileException -> String

jsonDecodeFile :: forall a. FromJSON a => Text -> IO a

Parses contents of a specified JSON file into a typed data

Data type should be specified with a type annotation:

Example:

dt <- jsonDecodeFile "path/to/foo.json" :: IO Foo

Data must be an instance of FromJSON

File contents are decoded as UTF-8

Throws an exception if file cannot be read or data cannot be decoded

Arguments:

• path :: Text: Path to JSON file

Return value: Decoded data

data JSONDecodeError

Error for jsonDecodeText function

Constructors

JSONDecodeError

Fields

• jsonText :: Text

  Specified text

• message :: Text

  Decoding error

Instances

Show JSONDecodeError

Defined in VtUtils.JSON

Methods

showsPrec :: Int -> JSONDecodeError -> ShowS

show :: JSONDecodeError -> String

showList :: [JSONDecodeError] -> ShowS

jsonDecodeText :: forall a. FromJSON a => Text -> Either JSONDecodeError a

Parses a JSON Text string into a typed data

Data type should be specified with a type annotation:

Example:

let Right (dt :: Foo) = jsonDecodeText text

Data must be an instance of FromJSON

Returns an error if data cannot be decoded

Arguments:

• text :: Text: JSON Text string to parse

Return value: Decoded data or decoding error

data JSONDecodeTextIOException

Exception for jsonDecodeTextIO function

Constructors

JSONDecodeTextIOException

Fields

• err :: JSONDecodeError

  Decoding error

Instances

Show JSONDecodeTextIOException

Defined in VtUtils.JSON

Methods

showsPrec :: Int -> JSONDecodeTextIOException -> ShowS

show :: JSONDecodeTextIOException -> String

showList :: [JSONDecodeTextIOException] -> ShowS

Exception JSONDecodeTextIOException

Defined in VtUtils.JSON

Methods

toException :: JSONDecodeTextIOException -> SomeException

fromException :: SomeException -> Maybe JSONDecodeTextIOException

displayException :: JSONDecodeTextIOException -> String

jsonEncodeText :: ToJSON a => a -> Text

Encodes a data into a JSON Text string

Data must be an instance of ToJSON

Arguments:

• data :: ToJSON: some data that supports JSON serialization with Aeson

Return value: JSON Text string

data JSONGetError

Error for jsonGet function

Instances

Show JSONGetError

Defined in VtUtils.JSON

Methods

showsPrec :: Int -> JSONGetError -> ShowS

show :: JSONGetError -> String

showList :: [JSONGetError] -> ShowS

jsonGet :: forall a. FromJSON a => Value -> Text -> Either JSONGetError a

Extract the field value from the specified JSON object

Returns an error, if specified JSON Value is not a JSON object, if it does't contain a specified field, if field type is different from the one specified in type annotation

Data type should be specified with a type annotation:

let obj = object
        [ "foo" .= (42 :: Int)
        , "bar" .= ("baz" :: Text)
        ]
let Right (fooval :: Int) = jsonGet obj "foo"
let Right (barval :: Text) = jsonGet obj "bar"

Arguments:

• val :: Aeson.Value: JSON value, must be a JSON object
• field :: Text: Field name

Return value: Field value or an error

jsonUnwrapUnaryOptions :: Options

JSON options with unwrapUnaryRecords flag flipped to True