GraphQL.Value.FromValue

Literal GraphQL values.

Documentation

class FromValue a where

a can be converted from a GraphQL Value to a Haskell value.

The FromValue instance converts Value to the type expected by the handler function. It is the boundary between incoming data and your custom application Haskell types.

FromValue has a generic instance for converting input objects to records.

Methods

fromValue :: Value' ConstScalar -> Either Text a

Convert an already-parsed value into a Haskell value, generally to be passed to a handler.

fromValue :: (Generic a, GenericFromValue (Rep a)) => Value' ConstScalar -> Either Text a

Convert an already-parsed value into a Haskell value, generally to be passed to a handler.

Instances

FromValue Bool

Methods

fromValue :: Value' ConstScalar -> Either Text Bool

FromValue Double

Methods

fromValue :: Value' ConstScalar -> Either Text Double

FromValue Int32

Methods

fromValue :: Value' ConstScalar -> Either Text Int32

FromValue Text

Methods

fromValue :: Value' ConstScalar -> Either Text Text

FromValue v => FromValue [v]

Methods

fromValue :: Value' ConstScalar -> Either Text [v]

FromValue v => FromValue (Maybe v)

Methods

fromValue :: Value' ConstScalar -> Either Text (Maybe v)

FromValue v => FromValue (NonEmpty v)

Methods

fromValue :: Value' ConstScalar -> Either Text (NonEmpty v)

prop_roundtripValue :: forall a. (Eq a, ToValue a, FromValue a) => a -> Bool

Anything that can be converted to a value and from a value should roundtrip.

wrongType :: (MonadError Text m, Show a) => Text -> a -> m b

Throw an error saying that value does not have the expected type.