NAME

HTML::FormFu::Manual::Cookbook - Cooking with HTML::FormFu

DESCRIPTION

Miscellaneous useful recipes for use with HTML::FormFu

GETTING STARTED

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.

BUILDING A FORM

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.

MODIFYING A FORM

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()"

FORM VALIDATION

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.

Both the above attributes are documented further in HTML::FormFu::Constraint.

HTML MARKUP

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

DISPLAY

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.

ADVANCED CUSTOMISATION

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.

PERFORMANCE

StackTrace

Are you using Catalyst::Plugin::StackTrace? This is known to cause performance problems in combination with HTML::FormFu and Template, and we advise disabling it.

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;

FAQs

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

AUTHORS

Will Hawes wdhawes@gmail.com

Carl Franks cfranks@cpan.org

COPYRIGHT

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

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