HTML::FormFu::Manual::Cookbook - Cooking with HTML::FormFu Miscellaneous useful recipes for use with HTML::FormFu Some useful info for beginners.

Default search paths for config files
The current working directory ("cwd") (see "load_config_file" in HTML::FormFu). If you're using the "FormConfig" action attribute from Catalyst::Controller::HTML::FormFu, forms should be saved in "root/forms". See "SYNOPSIS" in Catalyst::Controller::HTML::FormFu and "config_file_path" in Catalyst::Controller::HTML::FormFu for further details.

YAML
Most examples given in the HTML::FormFu documentation use YAML syntax. You can use any configuration file type supported by Config::Any, but this author's preferred format is YAML. A form can be populated by a config file by calling "load_config_file" in HTML::FormFu with the filename as an argument. The config file is converted to a perl data-structure, and then passed to "populate" in HTML::FormFu. The config file must contain a hash-ref, with the keys corresponding to form method-names, and the values being the method arguments. For example, the following are equivalent: --- auto_fieldset: 1 elements: - name: foo - name: bar # the above YAML is equivalent to the following perl code $form->auto_fieldset(1); $form->elements([ { name => 'foo' }, { name => 'bar' }, ]); When writing your config file, remember that perl hashes are unordered and cannot have multiple keys with the same name. See "load_config_file" in HTML::FormFu and "populate" in HTML::FormFu for more details. See <http://www.yaml.org/spec/> for the YAML specification.

Quick single-file prototypes
You can run the following script to quickly view a form's markup - replace the contents of the "__DATA__" section with your own YAML config. #!/usr/bin/perl use strict; use warnings; use HTML::FormFu; use YAML::Syck qw( Load ); my $form = HTML::FormFu->new; my $yaml = do { local $/; <DATA> }; my $data = Load($yaml); $form->populate($data); print $form; __DATA__ --- auto_fieldset: 1 elements: - type: Text name: foo

Unsupported HTML tags
You can use the HTML::FormFu::Element::Block element, and set the tag to create any arbitrary pair of tags. --- elements: - type: Block tag: span content_xml: "<b>Hi!</b>" You can use "content" in HTML::FormFu::Element::Block, "content_xml" in HTML::FormFu::Element::Block or "content_loc" in HTML::FormFu::Element::Block to add any content you wish, or use "element" in HTML::FormFu::Element::Block to add elements.

Insert a new field before existing form fields
See "insert_before" in HTML::FormFu and "insert_after" in HTML::FormFu. my $fieldset = $form->get_element({ type => 'Fieldset' }); $fieldset->insert_before( $form->element(\%specs), $form->get_field($name) ); Another way to approach the problem is to use multiple config files, and decide which to load at runtime: # user_edit.yml --- elements: - type: Text name: email # user_username.yml --- elements: - type: Text name: username # user_register.yml --- load_config_file: - user_username.yml - user_edit.yml # create a user edit form, with only the email field $form->load_config_file( 'user_edit.yml' ); # create a user registration form with username and email fields $form->load_config_file( 'user_register.yml' );

From and Field attributes
You can add any arbitrary attributes to a form with "attributes" in HTML::FormFu, or to any element with "attributes" in HTML::FormFu::Element. --- attributes_xml: onsubmit: "js_function()" elements: - type: Text name: foo attributes_xml: onchange: "js_function()"

Check valid dates
Use HTML::FormFu::Inflator::DateTime. When the inflator is processed, it will try to create a DateTime object. An error will be returned if the supplied values do not make a valid date.

Check valid URI / URLs
HTML::FormFu::Constraint::Regex supports Regexp::Common regular expressions: --- elements: - type: Text name: uri constraints: - type: Regex common: [ URI, HTTP, { '-scheme': 'ftp|https?' ]

Implement a custom constraint / validator
If HTML::FormFu::Constraint::Callback or HTML::FormFu::Validator::Callback isn't sufficient for your needs, you can create your own class that inherits from HTML::FormFu::Constraint or HTML::FormFu::Validator, respectively. It should implement a "validate_value" method, which returns true is the value is valid, or false otherwise. package My::Custom::Validator; use strict; use base 'HTML::FormFu::Validator'; sub validate_value { my ( $self, $value, $params ) = @_; return 1 if value_is_valid( $value ); return; } 1; Then add your custom validator to the form: --- elements: - type: Text name: foo validators: - '+My::Custom::Validator'

Constrain one form field based on the value of another
For example, you have a radiogroup and several text fields, with different text fields being required depending on the value of the radiogroup. This is achieved using the "when" attribute of a constraint: constraints: - type: Length min: 8 when: field: bar values: [ 1, 3, 5 ] In the above example, the Length constraint is only processed when the form field named "bar" has a value of either 1, 3 or 5. You can also test for a negative condition using the "not" attribute: constraints: - type: Length min: 8 when: field: bar values: [ 1, 3, 5 ] not: 1 Now the constraint will be processed only if the value of field "bar" is NOT 1, 3 or 5. Note: if you rely on the value of a checkbox for a when-restricted contraint, you might want to consider setting "default_empty_value" for that checkbox. Take a look at HTML::FormFu::Element::_Field to learn more. Please read HTML::FormFu::Constraint for futher information.

Constrain one form field based on the return value of a callback
You can use the "when" attribute of a constraint also to decide using a callback if the constraint should be applied. For instance, the following (code) example shows a constraint being applied only if the value of another field contains a pattern my $apply_if_pattern = sub { my $params = shift; return 1 if $params->{other_field} =~ m/\A ice_cream \z/xms; return 0; } $field->{constraints} = { type => 'Required', when => { callback => $apply_if_pattern, } } Please read HTML::FormFu::Constraint for futher information.

Indented HTML
Use HTML::FormFu::OutputProcessor::Indent: --- output_processors: - Indent

Add a blank div (e.g. for AJAX purposes)
Simply add a Block element in the relevant place, it defaults to a "DIV" tag. --- elements: - type: Text name: user - type: Block id: foo - type: Text name: email

Custom error messages
If you want to display an error message due to an error in your own code, such as a database check; something which isn't implemented as a Constraint or Validator; you can use a Callback Constraint. If you don't provide your own callback routine, the default callback will always pass, regardless of user input. You can take advantage of this by setting force_errors, to display it's error message when needed. Example config: --- elements: - type: Text - name: email - constraints: type: Callback message: 'Email address already in use' Example usage: if ( $@ =~ m/duplicate entry for key 'email'/i ) { $form->get_field('email') ->get_constraint({ type => 'Callback' }) ->force_errors(1); $form->process; # then redisplay the form as normal }

Add a popup hint to a field
Some visual browsers (including IE6/7, Firefox, Opera 9) display a tooltip when a user hovers their mouse pointer over an HTML element with a "title" tag. Aural browsers may try to turn the content into speech. You can take advantage of this behaviour to provide a hint to the user about how to complete a form field. elements: - type: Text name: country_name label: Country Name attributes: title: Name of country The above will provide a hint when the "country_name" field receives focus. Or you could provide the hint for the container tag around both field and label: elements: - type: Text name: country_name label: Country Name container_attributes: title: Name of country

Display filtered values
If you have a Filter on a field, such as HTML::FormFu::Filter::Whitespace to strip leading / trailing whitespace, then if you redisplay the form the field is normally populated with the value the user originally entered. If you would like the field to contain the filtered value, use "render_processed_value" in HTML::FormFu.

Installing the TT templates
It only makes sense to use the template files if you plan on customising them, as the default "string" render-method is faster. If you're using the Catalyst web framework, install Catalyst::Controller::HTML::FormFu and run the following command: $ script/myapp_create.pl HTML::FormFu This will create a directory, "root/formfu", containing the HTML::FormFu template files. If you use Catalyst::Controller::HTML::FormFu as a base class and you don't set HTML::FormFu's INCLUDE_PATH yourself, it will automatically be set to "root/formfu" if that directory exists. If you're not using Catalyst, you can create the template files by running the following command: $ html_formfu_deploy.pl <target-directory> Take note that if you choose to customise your own copy of HTML::FormFu's template files, you'll need to keep track of the "Changes" file, when updating HTML::FormFu, so that you can update your own templates if the core templates are updated.

Catalyst::Plugin::StackTrace
If you're using Catalyst::Plugin::StackTrace, make sure you're using at least version 0.09 - earlier versions had performance problems with "HTML::FormFu".

Template::Alloy
You can also use Template::Alloy instead of Template::Toolkit, it's mostly compatible, and in many cases provides a reasonable speed increase. You can do this either by setting the "HTML_FORMFU_TEMPLATE_ALLOY" environment variable to a true value, or by passing "TEMPLATE_ALLOY" to "tt_args" in HTML::FormFu: tt_args: TEMPLATE_ALLOY: 1 COMPILE_DIR: /tmp COMPILE_PERL: 1 Template::Alloy's caching is off by default. Switch it on by setting either "COMPILE_EXT" or "COMPILE_DIR". If you're running under a persistent environment such as modperl or fastcgi, you should also set "COMPILE_PERL" to compile the cached templates down to perl code. Of cource, if you wish you can still use Template::Toolkit to process your own application templates, letting Template::Alloy process just the HTML::FormFu templates.

HTML:FormFu::Preload
To reduce the runtime for each form that uses a previously unused element or processor - at the expense of greater memory usage - you can preload all FormFu modules - this is only recommended for persistent environments such as modperl or fastcgi: use HTML::FormFu::Preload;

Force an element to always have a certain value
See the following: "retain_default" in HTML::FormFu::Element::_Field, "force_default" in HTML::FormFu::Element::_Field Will Hawes "wdhawes@gmail.com" Carl Franks "cfranks@cpan.org" This document is free, you can redistribute it and/or modify it under the same terms as Perl itself.