Safe Haskell | Safe-Inferred |
---|---|

Language | Haskell98 |

End-user interface - provides the main functionality for form creation and validation. For an interface for front-end implementation, see View.

- type Formlet v m a = Maybe a -> Form v m a
- type Form v m a = FormTree m v m a
- data SomeForm v m = forall a . SomeForm (FormTree Identity v m a)
- (.:) :: Monad m => Text -> Form v m a -> Form v m a
- text :: Formlet v m Text
- string :: Monad m => Formlet v m String
- stringRead :: (Monad m, Read a, Show a) => v -> Formlet v m a
- choice :: (Eq a, Monad m) => [(a, v)] -> Formlet v m a
- choice' :: Monad m => [(a, v)] -> Maybe Int -> Form v m a
- choiceWith :: (Eq a, Monad m) => [(Text, (a, v))] -> Formlet v m a
- choiceWith' :: Monad m => [(Text, (a, v))] -> Maybe Int -> Form v m a
- groupedChoice :: (Eq a, Monad m) => [(Text, [(a, v)])] -> Formlet v m a
- groupedChoice' :: Monad m => [(Text, [(a, v)])] -> Maybe Int -> Form v m a
- groupedChoiceWith :: (Eq a, Monad m) => [(Text, [(Text, (a, v))])] -> Formlet v m a
- groupedChoiceWith' :: Monad m => [(Text, [(Text, (a, v))])] -> Maybe Int -> Form v m a
- bool :: Formlet v m Bool
- file :: Form v m (Maybe FilePath)
- optionalText :: Monad m => Maybe Text -> Form v m (Maybe Text)
- optionalString :: Monad m => Maybe String -> Form v m (Maybe String)
- optionalStringRead :: (Monad m, Read a, Show a) => v -> Maybe a -> Form v m (Maybe a)
- utcTimeFormlet :: Monad m => String -> String -> TimeZone -> Formlet Text m UTCTime
- localTimeFormlet :: Monad m => String -> String -> Formlet Text m LocalTime
- dateFormlet :: Monad m => String -> Formlet Text m Day
- timeFormlet :: Monad m => String -> Formlet Text m TimeOfDay
- optionalUtcTimeFormlet :: Monad m => String -> String -> TimeZone -> Maybe UTCTime -> Form Text m (Maybe UTCTime)
- optionalLocalTimeFormlet :: Monad m => String -> String -> Maybe LocalTime -> Form Text m (Maybe LocalTime)
- optionalDateFormlet :: Monad m => String -> Maybe Day -> Form Text m (Maybe Day)
- optionalTimeFormlet :: Monad m => String -> Maybe TimeOfDay -> Form Text m (Maybe TimeOfDay)
- check :: Monad m => v -> (a -> Bool) -> Form v m a -> Form v m a
- checkM :: Monad m => v -> (a -> m Bool) -> Form v m a -> Form v m a
- validate :: Monad m => (a -> Result v b) -> Form v m a -> Form v m b
- validateOptional :: Monad m => (a -> Result v b) -> Form v m (Maybe a) -> Form v m (Maybe b)
- validateM :: Monad m => (a -> m (Result v b)) -> Form v m a -> Form v m b
- conditions :: [a -> Result e b] -> a -> Result [e] a
- disable :: Form v m a -> Form v m a
- monadic :: m (Form v m a) -> Form v m a
- listOf :: Monad m => Formlet v m a -> Formlet v m [a]

# Documentation

type Form v m a = FormTree m v m a Source

Base type for a form.

The three type parameters are:

`v`

: the type for textual information, displayed to the user. For example, error messages are of this type.`v`

stands for "view".`m`

: the monad in which validators operate. The classical example is when validating input requires access to a database, in which case this`m`

should be an instance of`MonadIO`

.`a`

: the type of the value returned by the form, used for its Applicative instance.

Value-agnostic Form

(.:) :: Monad m => Text -> Form v m a -> Form v m a infixr 5 Source

Operator to set a name for a subform.

# Basic forms

stringRead :: (Monad m, Read a, Show a) => v -> Formlet v m a Source

Returns a `Formlet`

for a parseable and serializable value type

choice :: (Eq a, Monad m) => [(a, v)] -> Formlet v m a Source

Returns a `Formlet`

for a value restricted to
the provided list of value-message tuples

choiceWith :: (Eq a, Monad m) => [(Text, (a, v))] -> Formlet v m a Source

Allows you to assign your own values: these values will be used in the
resulting HTML instead of the default `[0 ..]`

. This fixes some race
conditions that might otherwise appear, e.g. if new choice items are added to
some database while a user views and submits the form...

choiceWith' :: Monad m => [(Text, (a, v))] -> Maybe Int -> Form v m a Source

A version of `choiceWith`

for when there is no good `Eq`

instance.

groupedChoice :: (Eq a, Monad m) => [(Text, [(a, v)])] -> Formlet v m a Source

Returns a `Formlet`

for named groups of choices.

groupedChoiceWith :: (Eq a, Monad m) => [(Text, [(Text, (a, v))])] -> Formlet v m a Source

Allows you to assign your own values: these values will be used in the
resulting HTML instead of the default `[0 ..]`

. This fixes some race
conditions that might otherwise appear, e.g. if new choice items are added to
some database while a user views and submits the form...

groupedChoiceWith' :: Monad m => [(Text, [(Text, (a, v))])] -> Maybe Int -> Form v m a Source

Low-level support for grouped choice.

# Optional forms

optionalText :: Monad m => Maybe Text -> Form v m (Maybe Text) Source

Create a text form with an optional default text which returns nothing if no optional text was set, and no input was retrieved.

optionalString :: Monad m => Maybe String -> Form v m (Maybe String) Source

Identical to `optionalText`

, but uses Strings

optionalStringRead :: (Monad m, Read a, Show a) => v -> Maybe a -> Form v m (Maybe a) Source

Identical to `optionalText`

for parseable and serializable values.

# Date/time forms

# Validation and transformation

:: Monad m | |

=> v | Error message (if fail) |

-> (a -> Bool) | Validating predicate |

-> Form v m a | Form to validate |

-> Form v m a | Resulting form |

Validate the results of a form with a simple predicate

Example:

check "Can't be empty" (not . null) (string Nothing)

checkM :: Monad m => v -> (a -> m Bool) -> Form v m a -> Form v m a Source

Version of `check`

which allows monadic validations

validate :: Monad m => (a -> Result v b) -> Form v m a -> Form v m b Source

This is an extension of `check`

that can be used to apply transformations
that optionally fail

Example: taking the first character of an input string

head' :: String -> Result String Char head' [] = Error "Is empty" head' (x : _) = Success x char :: Monad m => Form m String Char char = validate head' (string Nothing)

validateOptional :: Monad m => (a -> Result v b) -> Form v m (Maybe a) -> Form v m (Maybe b) Source

Same as `validate`

, but works with forms of the form:

Form v m (Maybe a)

.

Example: taking the first character of an optional input string

head' :: String -> Result String Char head' [] = Error "Is empty" head' (x : _) = Success x char :: Monad m => Form m String (Maybe Char) char = validateOptional head' (optionalString Nothing)

validateM :: Monad m => (a -> m (Result v b)) -> Form v m a -> Form v m b Source

Version of `validate`

which allows monadic validations

:: [a -> Result e b] | Any |

-> a | If all validation functions pass, parameter will be re-wrapped with a |

-> Result [e] a | List of errors is guaranteed to be in the same order as inputed validations functions. So, conditions [even, greaterThan 0] -1 is specified to return Error ["must be even", "must be greater than 0"] and not Error ["must be greater than 0", "must be even"] . |

Allows for the composition of independent validation functions.

For example, let's validate an even integer between 0 and 100:

form :: Monad m => Form Text m FormData ... -- some fields <*> "smallEvenInteger" .: validate (notEmpty >=> integer >=> even >=> greaterThan 0 >=> lessThanOrEq 100) (text Nothing) ... -- more fields

where

notEmpty :: IsString v => Text -> Result v Text integer :: (Integral a, IsString v) => Text -> Result v a greaterThan 0 :: (Num a, Ord a, Show a) => a -> Result Text a lessThanOrEq 0 :: (Num a, Ord a, Show a) => a -> Result Text a even :: Integer -> Result Text Integer

.

This will validate our smallEvenInteger correctly, but there is a problem. If a user enters an odd number greater than 100, only

"number must be even"

will be returned. It would make for a better user experience if

["number must be even", "number must be less than 100"]

was returned instead. This can be accomplished by rewriting our form to be:

form :: Monad m => Form [Text] m FormData ... -- some fields <*> "smallEvenInteger" .: validate (notEmpty >=> integer >=> conditions [even, greaterThan 0, lessThanOrEq 100]) (text Nothing) ... -- more fields

.

If we want to collapse our list of errors into a single `Text`

, we can do something like:

form :: Monad m => Form Text m FormData ... -- some fields <*> "smallEvenInteger" .: validate (notEmpty >=> integer >=> commaSeperated . conditions [even, greaterThan 0, lessThanOrEq 100]) (text Nothing) ... -- more fields

where

commaSeperated :: (Result [Text] a) -> (Result Text a)

.