A FieldError represents an error that happened during a FieldValidation. Here are the main ones :

MissingField          -- When the `Field` cannot be found
WrongType             -- When the `Value` has a different type
CustomError yourError -- Your type of error

A FieldValidation represents the Validation of a Field

Returns a failed FieldValidation

Returns a failed FieldValidation using a CustomError

Returns a successful FieldValidation

Helps creating a basic FieldValidation function

type YourError
    = MustBeEmpty


emptyValidation : String -> FieldValidation YourError String
emptyValidation =
    validation MustBeEmpty String.isEmpty

Helps validating a String Value. If the Value has a different type, fails with a WrongType FieldError.

type YourError
    = MustBeEmpty


validateEmptyField : Value -> FieldValidation YourError String
validateEmptyField =
    stringValid (validation MustBeEmpty String.isEmpty)

Helps validating a Bool Value. If the Value has a different type, fails with a WrongType FieldError.

type YourError
    = MustBeChecked


validateCheckedField : Value -> FieldValidation YourError Bool
validateCheckedField =
    boolValid (validation MustBeChecked ((==) True))

Helps validating a String that can be cast into an Int. If the String cannot be cast, fails with a NotInt FieldError.

doYourValidation : Int -> FieldValidation err a


validateField : Value -> FieldValidation err a
validateField =
    stringValid (int (doYourValidation))

Helps validating a String that can be cast into a Float. If the String cannot be cast, fails with a NotFloat FieldError.

doYourValidation : Float -> FieldValidation err a


validateField : Value -> FieldValidation err a
validateField =
    stringValid (float (doYourValidation))

Helps validating a String that is not empty. If the Stringis empty, fails with an EmptyString FieldError.

doYourValidation : String -> FieldValidation err a


validateField : Value -> FieldValidation err a
validateField =
    stringValid (notEmpty (doYourValidation))

Helps validating a String that has a specific length (> low && < high). If the String has a different length, fails with a WrongLength FieldError.

doYourValidation : String -> FieldValidation err a


validateField : Value -> FieldValidation err a
validateField =
    stringValid (length low high (doYourValidation))

Helps validating a String that is an email. If the Stringis not an email, fails with a NotEmail FieldError.

doYourValidation : String -> FieldValidation err a


validateField : Value -> FieldValidation err a
validateField =
    stringValid (email (doYourValidation))

Helps validating two String Values that match. If the Strings don't match, fails with a PasswordNotEqual FieldError.

doYourValidation : String -> FieldValidation err a


validateField : Value -> Value -> FieldValidation err a
validateField =
    passwordMatch (doYourValidation)

A FormError represents an error that happened during a FormValidation. It's basically a wrapper around the FieldError with the key associated to the Field

A FormValidation represents the Validation of a Form

Returns a successful FormValidation

Converts a FormError into a Tuple

Validate represents a function that validates a Form. It takes a Group of Fields and returns a FormValidation

Validates a required Field. This is the basic use case and will always validate the Field

...
    |> required fields comparable doYourValidation
    ...

Hardcodes a value. This is useful when you need to harcode a specific value during the validation process

...
    |> hardcoded yourHardcodedValue
    ...

Validates an optional Field. This will use the validation function if the Field is not empty or use the default value otherwise. Only works on String Value

...
    |> optional fields comparable doYourValidation yourDefaultValue
    ...

optional is equivalent to a specific required:

...
    |> required
        fields
        comparable
        (stringValid <|
            \str ->
                if String.isEmpty str then
                    success yourDefaultValue
                else
                    doYourValidation str
        )
    ...

Validates an optional Field with a Maybe. Same logic than with optional but the default value is Nothing and the validated value is Just

...
    |> optionalMaybe fields comparable doYourValidation
    ...

Validates two Fields together. The validation function takes two Field Values and returns one result. It is useful when you need to validate one Field that depends on another, but you only need to store one result

...
    |> twoFields fields comparable1 comparable2 doYourValidation
    ...

Validates a Group of Fields. This can be useful in many different cases but mainly when you need to nest a validation process

 ...
    |> fieldGroup fields comparable doYourValidation
    ...

Validates a required Field (binding)

...
    |> required1 fields comparable doYourValidation
    ...

Hardcodes a value for a Field (binding)

...
    |> hardcoded1 yourHardcodedValue
    ...

Validates an optional Field (binding)

...
    |> optional1 fields comparable doYourValidation yourDefaultValue
    ...

Validates an optional Field with a Maybe (binding)

...
    |> optionalMaybe1 fields comparable doYourValidation
    ...

Validates two Fields together (binding)

...
    |> twoFields1 fields comparable1 comparable2 doYourValidation
    ...

Validates a Group of Fields (binding)

 ...
    |> fieldGroup fields comparable doYourValidation
    ...