Ditto.Backend

This module contains two classes. FormInput is a class which is parameterized over the input type used to represent form data in different web frameworks. There should be one instance for each framework, such as Happstack, Snap, WAI, etc.

The FormError class is used to map error messages into an application specific error type.

Documentation

data CommonFormError input

an error type used to represent errors that are common to all backends

These errors should only occur if there is a bug in the ditto-* packages. Perhaps we should make them an Exception so that we can get rid of the FormError class.

Constructors

InputMissing FormId

NoStringFound input

NoFileFound input

MultiFilesFound input

MultiStringsFound input

MissingDefaultValue

Instances

Eq input => Eq (CommonFormError input)

Defined in Ditto.Backend

Methods

(==) :: CommonFormError input -> CommonFormError input -> Bool

(/=) :: CommonFormError input -> CommonFormError input -> Bool

Ord input => Ord (CommonFormError input)

Defined in Ditto.Backend

Methods

compare :: CommonFormError input -> CommonFormError input -> Ordering

(<) :: CommonFormError input -> CommonFormError input -> Bool

(<=) :: CommonFormError input -> CommonFormError input -> Bool

(>) :: CommonFormError input -> CommonFormError input -> Bool

(>=) :: CommonFormError input -> CommonFormError input -> Bool

max :: CommonFormError input -> CommonFormError input -> CommonFormError input

min :: CommonFormError input -> CommonFormError input -> CommonFormError input

Show input => Show (CommonFormError input)

Defined in Ditto.Backend

Methods

showsPrec :: Int -> CommonFormError input -> ShowS

show :: CommonFormError input -> String

showList :: [CommonFormError input] -> ShowS

commonFormErrorStr

Arguments

:: (input -> String)

show input in a format suitable for error messages

-> CommonFormError input

a CommonFormError

-> String

some default error messages for CommonFormError

commonFormErrorText

Arguments

:: (input -> Text)

show input in a format suitable for error messages

-> CommonFormError input

a CommonFormError

-> Text

some default error messages for CommonFormError

class FormError e where

A Class to lift a CommonFormError into an application-specific error type

Associated Types

type ErrorInputType e

Methods

commonFormError :: CommonFormError (ErrorInputType e) -> e

Instances

FormError Text

Defined in Ditto.Backend

Associated Types

type ErrorInputType Text :: Type

Methods

commonFormError :: CommonFormError (ErrorInputType Text) -> Text

class FormInput input where

Class which all backends should implement.

Minimal complete definition

getInputStrings, getInputFile

Associated Types

type FileType input

input is here the type that is used to represent a value uploaded by the client in the request.

Methods

getInputString :: (FormError error, ErrorInputType error ~ input) => input -> Either error String

Parse the input into a string. This is used for simple text fields among other things

getInputStrings :: input -> [String]

Should be implemented

getInputText :: (FormError error, ErrorInputType error ~ input) => input -> Either error Text

Parse the input value into Text

getInputTexts :: input -> [Text]

Can be overriden for efficiency concerns

getInputFile :: (FormError error, ErrorInputType error ~ input) => input -> Either error (FileType input)

Get a file descriptor for an uploaded file