NAME

       HTML::FormFu::Constraint - Constrain User Input

SYNOPSIS

           ---
           elements:
             - type: Text
               name: foo
               constraints:
                 - type: Length
                   min: 8
                   when:
                     field: bar
                     values: [ 1, 3, 5 ]
             - type: Text
               name: bar
               constraints:
                 - Integer
                 - Required
           constraints:
             - SingleValue

DESCRIPTION

       User input is processed in the following order:

       Filters
       Constraints
       Inflators
       Validators
       Transformers

       See "FORM LOGIC AND VALIDATION" in HTML::FormFu for further details.

       "constraints" in HTML::FormFu can be called on any form, block element (includes
       fieldsets) or field element.

       If called on a field element, no "name" argument should be passed.

       If called on a form or block element, if no "name" argument is provided, a new constraint
       is created for and added to every field on that form or block.

       See "FORM LOGIC AND VALIDATION" in HTML::FormFu for further details.

METHODS

   type
       Returns the "type" argument originally used to create the constraint.

   not
       If true, inverts the results of the constraint - such that input that would otherwise fail
       will pass, and vise-versa.

       This value is ignored by some constraints - see the documentation for individual
       constraints for details.

   only_on_reps
       Argument: \@repeatable_count

       For constraints added to fields within a Repeatable element, if "only_on_reps" is set, the
       constraint will only be run for fields whose repeatable_count matches one of these set
       values.

       Not available for the constraints listed in "Unsupported Constraints" in
       HTML::FormFu::Element::Repeatable.

   message
       Arguments: $string

       Set the message which will be displayed if the constraint fails.

   message_xml
       Arguments: $string

       Variant of "message" which ensures the value won't be XML-escaped.

   message_loc
       Arguments: $string

       Variant of "message" which uses localize to create the message.

   localize_args
       Provide arguments that should be passed to localize to replace "[_1]", "[_2]", etc. in the
       localized string.

   force_errors
       See "force_errors" in HTML::FormFu for details.

   parent
       Returns the field object that the constraint is associated with.

   form
       Returns the HTML::FormFu object that the constraint's field is attached to.

   name
       Shorthand for "$constraint->parent->name"

   when
       Defines a condition for the constraint. Only when the condition is fullfilled the
       constraint will be applied.

       This method expects a hashref.

       The "field" or "callback" must be supplied, all other fields are optional.

       If "value" or "values" is not supplied, the constraint will pass if the named field's
       value is true.

       The following keys are supported:

       field
           Nested-name of form field that shall be checked against - if "when-"{value}> is set,
           the "when" condition passes if the named field's value matches that, otherwise the
           "when" condition passes if the named field's value is true.

       fields
           Array-ref of nested-names that shall be checked. The "when" condition passes if all
           named-fields' values pass, using the same rules as "field" above.

       any_field
           Array-ref of nested-names that shall be checked. The "when" condition passes if any
           named-fields' values pass, using the same rules as "field" above.

       value
           Expected value in the form field 'field'

       values
           Array of multiple values, one must match to fullfill the condition

       not Inverts the when condition - value(s) must not match

       callback
           A callback subroutine-reference or fully resolved subroutine name can be supplied to
           perform complex checks. An hashref of all parameters is passed to the callback sub. In
           this case all other keys are ignored, including not.  You need to return a true value
           for the constraint to be applied or a false value to not apply it.

           The callback subroutine receives 2 arguments:

           1.      $params (hashref of all submitted parameters)

           2.      $constraint (the Constraint object)

EXPERIMENTAL METHODS

   fetch_error_message
       Return value: $string

       Attempt to return the error message that would be used if this constraint generated an
       error.

       This will generally be correct for simple constraints with a fixed message or which use a
       placeholder from a known value, such as "min" in HTML::FormFu::Constraint::Min.  This will
       generally "not" return the correct message for constraints which use "others" in
       HTML::FormFu::Role::Constraint::Others, where the field with an error is not known without
       actually fully processing a form submission.

CORE CONSTRAINTS

       HTML::FormFu::Constraint::AllOrNone
       HTML::FormFu::Constraint::ASCII
       HTML::FormFu::Constraint::AutoSet
       HTML::FormFu::Constraint::Bool
       HTML::FormFu::Constraint::Callback
       HTML::FormFu::Constraint::CallbackOnce
       HTML::FormFu::Constraint::DateTime
       HTML::FormFu::Constraint::DependOn
       HTML::FormFu::Constraint::Email
       HTML::FormFu::Constraint::Equal
       HTML::FormFu::Constraint::File
       HTML::FormFu::Constraint::File::MIME
       HTML::FormFu::Constraint::File::MaxSize
       HTML::FormFu::Constraint::File::MinSize
       HTML::FormFu::Constraint::File::Size
       HTML::FormFu::Constraint::Integer
       HTML::FormFu::Constraint::Length
       HTML::FormFu::Constraint::MaxLength
       HTML::FormFu::Constraint::MaxRange
       HTML::FormFu::Constraint::MinLength
       HTML::FormFu::Constraint::MinRange
       HTML::FormFu::Constraint::MinMaxFields
       HTML::FormFu::Constraint::Number
       HTML::FormFu::Constraint::Printable
       HTML::FormFu::Constraint::Range
       HTML::FormFu::Constraint::Regex
       HTML::FormFu::Constraint::Required
       HTML::FormFu::Constraint::Set
       HTML::FormFu::Constraint::SingleValue
       HTML::FormFu::Constraint::Word

NON-CORE CONSTRAINTS AVAILABLE ON CPAN

       HTML::FormFu::Constraint::reCAPTCHA

CAVEATS

       See "Unsupported Constraints" in HTML::FormFu::Element::Repeatable for a list of
       constraints that won't work within HTML::FormFu::Element::Repeatable.

AUTHOR

       Carl Franks, "cfranks@cpan.org"

       Based on the original source code of HTML::Widget::Constraint, by Sebastian Riedel,
       "sri@oook.de".

LICENSE

       This library is free software, you can redistribute it and/or modify it under the same
       terms as Perl itself.