NAME
HTML::FormHandler::Manual::Cookbook - FormHandler use recipes
SYNOPSIS
Collection of use recipes for HTML::FormHandler
No form file, no template file...
I had to create a tiny little form this week for admins to enter a comment, and it seemed silly to have to create a form file and a template file. I remembered that you can set the TT 'template' to a a string reference and not use a template at all, which is nice when FormHandler will create the form HTML for you anyway.
sub comment : Chained('base_sub') PathPart('comment') Args(0) {
my ( $self, $c ) = @_;
my $form = HTML::FormHandler->new( field_list =>
[ comment => { type => 'Text', size => 60 },
submit => {type => 'Submit'} ] );
$form->process($c->req->params);
if ( $form->validated ) {
$self->admin_log( $c, "Admin::Queue", "admin comment",
$form->field('comment')->value );
$c->flash( message => 'Comment added' );
$c->res->redirect( $c->stash->{urilist}->{view} );
}
my $rendered_form = $form->render;
$c->stash( template => \$rendered_form );
}This creates the form on the fly with a comment field and a submit button, renders it using the default TT wrappers, then logs the comment. No other files at all....
FormHandler isn't really necessary for validation here, but it does make it possible to have a simple, standalone method.
Dynamically change the active fields
A common use case is for forms with some fields that should be displayed in some circumstances and not in others. There are a number of ways to do this. One way is to use the 'field_list' method:
sub field_list {
my $self = shift;
my @fields;
<build list of fields>
return \@fields;
}This only happens at form construction time, however. Another method that works is to define all of the possible fields in your form, and mark some of them 'inactive';
package MyApp::Variable::Form;
use HTML::FormHandler::Moose;
extends 'HTML::FormHandler';
has_field 'foo';
has_field 'bar' => ( inactive => 1 );
1;Then you can mark them active using a Moose method modifier on 'set_active'.
before 'set_active' => sub {
my $self = shift;
$self->active(['foo', bar']) if ( <some_condition> );
};Or on the 'process' call:
$form->process( params => $params, active => ['foo', 'bar'] );Fields set to active with the form's 'active' modifier (but not on new) will be automatically set back to inactive when the form is cleared, so there's no need to reset.
If you want the fields activated for the life of an object, set active on new:
my $form = MyApp::Form::User->new( active => ['opt_in', 'active']);Add custom attributes to FormHandler fields
If you want to add custom attributes to the FormHandler fields but don't want to subclass all the fields, you can apply a role containing the new attributes to an HTML::FormHandler::Field in your form.
Use the form attribute 'field_traits' to apply a role to the base field class. Use 'traits' on the individual fields to apply a role to field instances.
package MyApp::Form::Test;
use HTML::FormHandler::Moose;
extends 'HTML::FormHandler';
has_field 'foo' => ( traits => ['MyApp::TraitFor::Test'] );
has '+field_traits' => ( default => sub { ['Some::Trait', 'Another::Trait'] } );
Or set the traits on new:
my $form = MyApp::Form::User->new( field_traits => ['MyApp::TraitFor::Test'] );
my $form = MyApp::Form::User->new(
field_list => [ '+foo' => { traits => [...] } ]);Select lists
If you want to set the default value of a select field to 0 (or some other default):
sub default_license {
my ( $self, $field, $item ) = @_;
return 0 unless $item && $item->license_id;
return $item->license_id;
}If the table defining the choices for a select list doesn't include a 'no choice' choice, in your template:
[% f = form.field('subject_class') %]
<select id="select_sc" name="[% f.name %]">
<option value="">--- Choose Subject Class---</option>
[% FOR option IN f.options %]
<option value="[% option.value %]"
[% IF option.value == f.fif %]selected="selected"[% END %]>
[% option.label | html %]</option>
[% END %]
</select>Or customize the select list in an 'options_' method:
sub options_country {
my $self = shift;
return unless $self->schema;
my @rows =
$self->schema->resultset( 'Country' )->
search( {}, { order_by => ['rank', 'country_name'] } )->all;
return [ map { $_->digraph, $_->country_name } @rows ];
}The database and FormHandler forms
If you have to process the input data before saving to the database, and this is something that would be useful in other places besides your form, you should do that processing in the DBIx::Class result class.
If the pre-processing is only relevant to HTML form input, you might want to do it in the form by setting a flag to prevent database updates, performing the pre-processing, and then updating the database yourself.
has_field 'my_complex_field' => ( type => 'Text', noupdate => 1 );The 'noupdate' flag is set in order to skip an attempt to update the database for this field (it would not be necessary if the field doesn't actually exist in the database...). You can process the input for the non-updatable field field in a number of different places, depending on what is most logical. Some of the choices are:
1) validate (for the form or field)
2) validate_model
3) model_updateWhen the field is flagged 'writeonly', the value from the database will not be used to fill in the form (put in the $form->fif hash, or the field $field->fif), but a value entered in the form WILL be used to update the database.
If you want to enter fields from an additional table that is related to this one in a 'single' relationship, you can use the DBIx::Class 'proxy' feature to create accessors for those fields.
Set up form base classes or roles for your application
You can add whatever attributes you want to your form classes. Maybe you want to save a title, or a particular navigation widget. You could even save bits of text, or retrieve them from the database. Sometimes doing it this way would be the wrong way. But it's your form, your choice. In the right circumstances, it might provide a way to keep code out of your templates and simplify your controllers.
package MyApp::Form::Base;
use Moose;
extends 'HTML::FormHandler::Model::DBIC';
has 'title' => ( isa => 'Str', is => 'rw' );
has 'nav_bar' => ( isa => 'Str', is => 'rw' );
sub summary {
my $self = shift;
my $schema = $self->schema;
my $text = $schema->resultset('Summary')->find( ... )->text;
return $text;
}
1;Then:
package MyApp::Form::Whatsup;
use Moose;
extends 'MyApp::Form::Base';
has '+title' => ( default => 'This page is an example of what to expect...' );
has '+nav_bar' => ( default => ... );
...
1;And in the template:
<h1>[% form.title %]</h1>
[% form.nav_bar %]
<p><b>Summary: </b>[% form.summary %]</p>Or you can make these customizations Moose roles.
package MyApp::Form::Role::Base;
use Moose::Role;
...
package MyApp::Form::Whatsup;
use Moose;
with 'MyApp::Form::Role::Base';
...Split up your forms into reusable pieces
A person form:
package Form::Person;
use HTML::FormHandler::Moose;
extends 'HTML::FormHandler';
has_field 'name';
has_field 'telephone';
has_field 'email' => ( type => 'Email' );
sub validate_name {
....
}
no HTML::FormHandler::Moose;
1;An address form:
package Form::Address;
use HTML::FormHandler::Moose;
extends 'HTML::FormHandler';
has_field 'street';
has_field 'city';
has_field 'state' => ( type => 'Select' );
has_field 'zip' => ( type => '+Zip' );
sub options_state {
...
}
no HTML::FormHandler::Moose;
1;A form that extends them both:
package Form::Member;
use Moose;
extends ('Form::Person', 'Form::Address');
use namespace::autoclean;
1;Or if you don't need to use the pieces of your forms as forms themself, you can use roles;
package Form::Role::Address;
use HTML::FormHandler::Moose::Role;
has_field 'street';
has_field 'city';
has_field 'state' => ( type => 'Select' );
has_field 'zip' => ( type => '+Zip' );
sub options_state {
...
}
no HTML::FormHandler::Moose::Role;
1;You could make roles that are collections of validations:
package Form::Role::Member;
use Moose::Role;
sub check_zip {
...
}
sub check_email {
...
}
1;And if the validations apply to fields with different names, specify the 'set_validate' on the fields:
with 'Form::Role::Member';
has_field 'zip' => ( type => 'Integer', set_validate => 'check_zip' );Access a user record in the form
You might need the user_id to create specialized select lists, or do other form processing. Add a user_id attribute to your form:
has 'user_id' => ( isa => 'Int', is => 'rw' );Then pass it in when you process the form:
$form->process( item => $item, params => $c->req->parameters, user_id = $c->user->user_id );Handle extra database fields
If there is another database field that needs to be updated when a row is created, add an attribute to the form, and then process it with before 'update_model' .
In the form:
has 'hostname' => ( isa => 'Int', is => 'ro' );
before 'update_model' => sub {
my $self = shift;
$self->item->hostname( $self->hostname );
};Then just use an additional parameter when you create/process your form:
$form->process( item => $item, params => $params, hostname => $c->req->host );Record the user update
Use the 'before' or 'after' method modifiers for 'update_model', to flag a record as updated by the user, for example:
before 'update_model' => sub {
my $self = shift;
$self->item->user_updated if $self->item;
};Additional changes to the database
If you want to do additional database updates besides the ones that FormHandler does for you, the best solution would generally be to add the functionality to your result source or resultset classes, but if you want to do additional updates in a form you should use an 'around' method modifier and a transaction:
around 'update_model' => sub {
my $orig = shift;
my $self = shift;
my $item = $self->item;
$self->schema->txn_do( sub {
$orig->($self, @_);
<perform additional updates>
};
};Doing cross validation in roles
In a role that handles a number of different fields, you may want to perform cross validation after the individual fields are validated. In the form you could use the 'validate' method, but that doesn't help if you want to keep the functionality packaged in a role. Instead you can use the 'after' method modifier on the 'validate' method:
package MyApp::Form::Roles::DateFromTo;
use HTML::FormHandler::Moose::Role;
has_field 'date_from' => ( type => 'Date' );
has_field 'date_to' => ( type => 'Date' );
after 'validate' => sub {
my $self = shift;
$self->field('date_from')->add_error('From date must be before To date')
if $self->field('date_from')->value gt $self->field('date_to')->value;
};Changing required flag
Sometimes a field is required in one situation and not required in another. You can use a method modifier before 'validate_form':
before 'validate_form' => sub {
my $self = shift;
my $required = 0;
$required = 1
if( $self->params('field_name') eq 'something' );
$self->field('some_field')->required($required);
};This happens before the fields contain input or values, so you would need to look at the param value. If you need the validated value, it might be better to do these sort of checks in the form's 'validate' routine.
sub validate {
my $self = shift;
$self->field('dependent_field')->add_error("Field is required")
if( $self->field('some_field')->value eq 'something' &&
!$self->field('dependent_field')->has_value);
}In a Moose role you would need to use a method modifier instead.
after 'validate' => sub { ... };Don't forget the dependency list, which is used for cases where if any of one of a group of fields has a value, all of the fields are required.
AUTHOR
Gerda Shank, gshank@cpan.org
COPYRIGHT
This library is free software, you can redistribute it and/or modify it under the same terms as Perl itself.