Data.Validator

This module defines the Validator data type and helper functions for creating various validators.

Documentation

data Validator err subject

Datatype for checking if a validation holds for a subject.

• subject can be any data type for which assertions need to be checked.
• err can be any type representing an error, but it will only be possible to combine validators if the error type has a Semigroup instance.

Execute a validator by passing it to the validate function.

A Validator is both a Semigroup and a Monoid, making it possible to combine smaller validators into larger validators. A combined validator will accumulate errors from all of it's sub-validators.

Instances

Contravariant (Validator err)

Defined in Data.Validator

Methods

contramap :: (a -> b) -> Validator err b -> Validator err a

(>$) :: b -> Validator err b -> Validator err a

Semigroup err => Semigroup (Validator err subject)

Defined in Data.Validator

Methods

(<>) :: Validator err subject -> Validator err subject -> Validator err subject

sconcat :: NonEmpty (Validator err subject) -> Validator err subject

stimes :: Integral b => b -> Validator err subject -> Validator err subject

Monoid err => Monoid (Validator err subject)

Defined in Data.Validator

Methods

mempty :: Validator err subject

mappend :: Validator err subject -> Validator err subject -> Validator err subject

mconcat :: [Validator err subject] -> Validator err subject

validate :: Validator err subject -> subject -> Validation err subject

Runs a validator on a subject.

The result is a Validation containing all accumulated errors, or the subject wrapped in a Success value.

assert :: (subject -> Bool) -> err -> Validator err subject

Creates a validator that will return an error if the given predicate doesn't hold.

Since any predicate can be provided for checking if the subject satisfies certain conditions, this can be used to build your own custom validators.

Usage:

>>> let validator = assert (> 10) ["too small"]
>>> validate validator 11
Success 11

>>> validate validator 1
Failure ["too small"]

refute :: (subject -> Bool) -> err -> Validator err subject

Creates a validator that will return an error if the given predicate holds.

Since any predicate can be provided for checking if the subject satisfies certain conditions, this can be used to build your own custom validators.

Usage:

>>> let validator = refute (> 10) ["too big"]
>>> validate validator 11
Failure ["too big"]

>>> validate validator 1
Success 1

ifNothing :: err -> Validator err (Maybe a)

Returns an error if a Maybe is Nothing.

Usage:

>>> let validator = ifNothing ["Found nothing."]
>>> validate validator Nothing
Failure ["Found nothing."]

>>> validate validator (Just "Bob")
Success (Just "Bob")

ifLeft :: err -> Validator err (Either a b)

Returns an error if an Either contains a Left.

Usage:

>>> let validator = ifLeft ["Found left."]
>>> validate validator (Left 123)
Failure ["Found left."]

>>> validate validator (Right 456)
Success (Right 456)

class HasSize a where

Helper typeclass for checking if a value is empty.

Minimal complete definition

size

Methods

size :: a -> Int

isEmpty :: a -> Bool

Instances

HasSize [a]

Defined in Data.Validator

Methods

size :: [a] -> Int

isEmpty :: [a] -> Bool

HasSize (Seq a)

Defined in Data.Validator

Methods

size :: Seq a -> Int

isEmpty :: Seq a -> Bool

HasSize (Set a)

Defined in Data.Validator

Methods

size :: Set a -> Int

isEmpty :: Set a -> Bool

HasSize (Map k v)

Defined in Data.Validator

Methods

size :: Map k v -> Int

isEmpty :: Map k v -> Bool

ifEmpty :: HasSize subject => err -> Validator err subject

Returns an error if the function returns an "empty" value.

Usage:

>>> let validator = ifEmpty ["Empty."]
>>> validate validator []
Failure ["Empty."]

>>> validate validator [1, 2, 3]
Success [1,2,3]
>>> validate validator (Map.fromList [('a', 1), ('b', 2)])
Success (fromList [('a',1),('b',2)])

minSize :: HasSize subject => Int -> err -> Validator err subject

Returns an error if the value has a size smaller than required.

Usage:

>>> let validator = minSize 3 ["Too small."]
>>> validate validator []
Failure ["Too small."]
>>> validate validator [1, 2]
Failure ["Too small."]

>>> validate validator [1, 2, 3]
Success [1,2,3]

maxSize :: HasSize subject => Int -> err -> Validator err subject

Returns an error if the value has a size smaller than required.

Usage:

>>> let validator = maxSize 3 ["Too big."]
>>> validate validator [1, 2, 3, 4]
Failure ["Too big."]

>>> validate validator [1, 2, 3]
Success [1,2,3]

class IsOnlyWhiteSpace a where

Helper typeclass for checking if a value contains only whitespace characters.

Methods

isOnlyWhiteSpace :: a -> Bool

Instances

IsOnlyWhiteSpace String

Defined in Data.Validator

Methods

isOnlyWhiteSpace :: String -> Bool

IsOnlyWhiteSpace Text

Defined in Data.Validator

Methods

isOnlyWhiteSpace :: Text -> Bool

IsOnlyWhiteSpace Text

Defined in Data.Validator

Methods

isOnlyWhiteSpace :: Text -> Bool

ifBlank :: IsOnlyWhiteSpace subject => err -> Validator err subject

Returns an error if the function returns a value containing only whitespace.

Usage:

>>> let validator = ifBlank ["Only whitespace."]
>>> validate validator "   \t \n \r "
Failure ["Only whitespace."]

>>> validate validator "not empty"
Success "not empty"