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Data::MuForm - Data validator and form processor


version 0.05


Moo conversion of HTML::FormHandler, with more emphasis on data validation and a new way of rendering. The core behavior is basically the same as FormHandler, but some names have been changed, some functionality removed, some added. It will be necessary to change your forms to convert to MuForm, but it shouldn't be difficult.

See the manual at Data::MuForm::Manual, and in particular Data::MuForm::Manual::FormHandlerDiff if you're already using FormHandler.

    my $validator = MyApp::Form::Test->new;
    $validator->check( data => $params );
    my $form = MyApp::Form::User->new;
    $form->process( model => $row, params => $params );
    my $rendered_form = $form->render;
    if( $form->validated ) {
        # perform validated form actions
    else {
        # perform non-validated actions

An example of a custom form class:

    package MyApp::Form::User;
    use Moo;
    use Data::MuForm::Meta;
    extends 'Data::MuForm';

    has_field 'name' => ( type => 'Text' );
    has_field 'age' => ( type => 'Integer', apply => [ MinimumAge ] );
    has_field 'hobbies' => ( type => 'Multiple' );
    has_field 'address' => ( type => 'Compound' );
    has_field '' => ( type => 'Text' );
    has_field 'address.state' => ( type => 'Select' );
    has_field 'email' => ( type => 'Email' );

A dynamic form - one that does not use a custom form class - may be created using the 'field_list' attribute to set fields:

    my $validator = Data::MuForm->new(
        name => 'login_form',
        field_list => [
            'username' => {
                type  => 'Text',
                apply => [ { check => qr/^[0-9a-z]*\z/,
                   message => 'Contains invalid characters' } ],
            'password' => { apply => [ Password ] },


This documentation is mainly of Data::MuForm class attributes and methods. For general-purpose documentation see Data::MuForm::Manual.




Creating a form with 'new'

The new constructor takes name/value pairs:

    MyForm->new( action => $action );

No attributes are required on new. Normally you would pass in persistent attributes on 'new' (such as 'schema') and request/process related attributes on 'process'.

The form's fields will be built from the form definitions on new.

The 'field_list' is passed in on 'new' because fields are build at construction time. It can also be a method in the form class.

   field_list  - an array of field definitions

process & check

Data to be validated/processed:

   data     $validator->check( data => {} );
   params   $form->process( params => {} );

The 'init_values' hashref can be passed in, but can also be set in the form class:

   init_values - a hashref or object to provide initial values

Passed in on process with a DBIC model MuForm class:

   model     - database row object

See the model class for more information about 'model', 'model_id', 'model_class', and 'schema' (for the DBIC model). Data::MuForm::Model::DBIC.



Use the 'check' method to perform validation on your data:

    my $result = $validator->check( data => { ... } );

The 'result' returned from 'check' is $form->validated, but you can override the 'check_result' method in the form to return data in whatever format you wish.


Call the 'process' method on your form to perform validation and update. A database form must have either a model (row object) or a schema, model_id (row primary key), and model_class (usually set in the form). A non-database form requires only parameters.

   $form->process( model => $book, params => $c->req->parameters );
   $form->process( model_id => $model_id,
       schema => $schema, params => $c->req->parameters );
   $form->process( params => $c->req->parameters );

This process method returns the 'validated' flag ($form->validated). If it is a database form and the form validates, the database row will be updated.

After the form has been processed, you can get a parameter hashref suitable for using to fill in the form from $form->fif. A hash of inflated values (that would be used to update the database for a database form) can be retrieved with $form->value.

If you don't want to update the database, you can use the 'check' method instead.


Parameters are passed in when you call 'process'. HFH gets data to validate and store in the database from the params hash. If the params hash is empty, no validation is done, so it is not necessary to check for POST before calling $form->process. (Although see the 'posted' option for complications.)

Params can either be in the form of CGI/HTTP style params:

      user_name => "Joe Smith",
      occupation => "Programmer",
      'addresses.0.street' => "999 Main Street",
      '' => "Podunk",
      '' => "UT",
      'addresses.0.address_id' => "1",
      'addresses.1.street' => "333 Valencia Street",
      '' => "San Francisco",
      '' => "UT",
      'addresses.1.address_id' => "2",

or as structured data in the form of hashes and lists:

      addresses => [
            city => 'Middle City',
            country => 'GK',
            address_id => 1,
            street => '101 Main St',
            city => 'DownTown',
            country => 'UT',
            address_id => 2,
            street => '99 Elm St',
      'occupation' => 'management',
      'user_name' => 'jdoe',

CGI style parameters will be converted to hashes and lists for HFH to operate on.


Note that MuForm by default uses empty params as a signal that the form has not actually been submitted, and so will not attempt to validate a form with empty params. Most of the time this works OK, but if you have a small form with only the controls that do not return a post parameter if unselected (checkboxes and select lists), then the form will not be validated if everything is unselected. For this case you can either add a hidden field as an 'indicator', or use the 'submitted' flag:

   $form->process( submitted => ($c->req->method eq 'POST'), params => ... );

The 'submitted' flag also works to prevent validation from being performed if there are extra params in the params hash and it is not a 'POST' request.

Getting data out

fif (fill in form)

If you don't use MuForm rendering and want to fill your form values in using some other method (such as with HTML::FillInForm or using a template) this returns a hash of values that are equivalent to params which you may use to fill in your form.

The fif value for a 'title' field in a TT form:

   [% form.fif.title %]

Or you can use the 'fif' method on individual fields:

   [% form.field('title').fif %]

If you use MuForm to render your forms or field you probably won't use these methods.


Returns a hashref of all field values. Useful for non-database forms, or if you want to update the database yourself. The 'fif' method returns a hashref with the field names for the keys and the field's 'fif' for the values; 'value' returns a hashref with the field accessors for the keys, and the field's 'value' (possibly inflated) for the values.

Forms containing arrays to be processed with Data::MuForm::Field::Repeatable will have parameters with dots and numbers, like '', while the values hash will transform the fields with numbers to arrays.

Accessing and setting up fields

Fields are declared with a number of attributes which are defined in Data::MuForm::Field. If you want additional attributes you can define your own field classes (or apply a role to a field class - see Data::MuForm::Manual::Cookbook). The field 'type' (used in field definitions) is the short class name of the field class, used when searching the 'field_namespace' for the field class.


The most common way of declaring fields is the 'has_field' syntax. Using the 'has_field' syntax sugar requires use Data::MuForm::Meta; . See Data::MuForm::Manual::Intro

   use Moo;
   use Data::MuForm::Meta;
   has_field 'field_name' => ( type => 'FieldClass', .... );


A 'field_list' is an array of field definitions which can be used as an alternative to 'has_field' in small, dynamic forms to create fields.

    field_list => [
       field_one => {
          type => 'Text',
          required => 1
       field_two => 'Text,

The field_list array takes elements which are either a field_name key pointing to a 'type' string or a field_name key pointing to a hashref of field attributes. You can also provide an array of hashref elements with the name as an additional attribute. The field list can be set inside a form class, when you want to add fields to the form depending on some other state, although you can also create all the fields and set some of them inactive.

   sub field_list {
      my $self = shift;
      my $fields = $self->schema->resultset('SomeTable')->
                          search({user_id => $self->user_id, .... });
      my @field_list;
      while ( my $field = $fields->next )
         < create field list >
      return \@field_list;


You can add an additional field with $form->add_field.

    my $order = $form->field('foo')->order + 1;
       name => 'my_cb',
       type => 'Checkbox',
       order => $order,

It will be ordered as the last field unless you set the 'order' attribute. Form fields are automatically ordered by 5 (i.e. 5, 10, 15, etc).


A field can be marked 'inactive' and set to active at process time by specifying the field name in the 'active' array:

   has_field 'foo' => ( type => 'Text', inactive => 1 );
   my $form = MyApp::Form->new;
   $form->process( active => ['foo'] );

Or a field can be a normal active field and set to inactive at process time:

   has_field 'bar';
   my $form = MyApp::Form->new;
   $form->process( inactive => ['foo'] );

Fields specified as active/inactive on 'process' will have the flag flag cleared when the form is cleared (on the next process/check call).

The 'sorted_fields' method returns only active fields, sorted according to the 'order' attribute. The 'fields' method returns all fields.

   foreach my $field ( $self->all_sorted_fields ) { ... }

You can test whether a field is active by using the field 'is_active' and 'is_inactive' methods.


Use to look for field during form construction. If a field is not found with the field_namespace (or Data::MuForm/Data::MuFormX), the 'type' must start with a '+' and be the complete package name.


The array of fields, objects of Data::MuForm::Field or its subclasses. A compound field will itself have an array of fields, so this is a tree structure.


Returns those fields from the fields array which are currently active, ordered by the 'order' attribute. This is the method that returns the fields that are looped through when rendering.

field($name), subfield($name)

'field' is the method that is usually called to access a field:

    my $title = $form->field('title')->value;
    [% f = form.field('title') %]

    my $city = $form->field('')->value;

Since fields are searched for using the form as a base, if you want to find a sub field in a compound field method, the 'subfield' method may be more useful, since you can search starting at the current field. The 'chained' method also works:

    -- in a compound field --
    $self->field('media.caption'); # fails
    $self->field('media')->field('caption'); # works
    $self->subfield('media.caption'); # works


Create a 'build_field_id' sub in the form class to use a common method for constructing field ids.

    sub build_field_id {
       my ( $self, $field ) = @_;
       return $field->name . '_' . $self->id;

Constraints and validation

Most validation is performed on a per-field basis, and there are a number of different places in which validation can be performed.

See also Data::MuForm::Manual::Validation.

Class validation for individual fields

You can define a method in your class to perform validation on a field. This method is the equivalent of the field class validate method except it is in the validator/form class, so you might use this validation method if you don't want to create a field subclass.

It has access to the form ($self) and the field. This method is called after the field class 'validate' method, and is not called if the value for the field is empty ('', undef). (If you want an error message when the field is empty, use the 'required' flag and message or the form 'validate' method.) The name of this method can be set with 'set_validate' on the field. The default is 'validate_' plus the field name:

   sub validate_testfield { my ( $self, $field ) = @_; ... }

If the field name has dots they should be replaced with underscores.

Note that you can also provide a coderef which will be a method on the field:

   has_field 'foo' => ( methods => { validate => \&validate_foo } );


This is a form method that is useful for cross checking values after they have been saved as their final validated value, and for performing more complex dependency validation. It is called after all other field validation is done, and whether or not validation has succeeded, so it has access to the post-validation values of all the fields.

This is the best place to do validation checks that depend on the values of more than one field.

Accessing errors

Also see Data::MuForm::Manual::Errors.

Set an error in a field with $field->add_error('some error string');. Set a form error not tied to a specific field with $self->add_form_error('another error string');. The 'add_error' and 'add_form_error' methods call localization. If you want to skip localization for a particular error, you can use 'push_error' or 'push_form_errors' instead.

  has_errors - returns true or false
  error_fields - returns list of fields with errors
  errors - returns array of error messages for the entire form
  num_errors - number of errors in form

Each field has an array of error messages. (errors, has_errors, num_errors, clear_errors)


Compound fields also have an array of error_fields.

Clear form state

The clear method is called at the beginning of 'process' if the form object is reused, such as when it is persistent, or in tests. If you add other attributes to your form that are set on each request, you may need to either clear those yourself or ensure that they are always set on each process call.

Miscellaneous attributes


The form's name. Useful for multiple forms. Used for the form element 'id'. When 'field_prefix' is set it is used to construct the field 'id' and 'name'. The default is derived from the form class name.


An 'init_values' object or hashref may be used instead of the 'model' to pre-populate the values in the form. This can be useful when populating a form from default values stored in a similar but different object than the one the form is creating. It can be set in a variety of ways:

   my $form = MyApp::Form->new( init_values => { .... } );
   $form->process( init_values => {...}, ... );
   has '+init_values' => ( default => sub { { .... } } );
   sub init_values { my $self = shift; .... }

The method version is useful if the organization of data in your form does not map to an existing or database object in an automatic way, and you need to create a different type of object for initialization. (You might also want to do 'update_model' yourself.)

You can use both a 'model' and an 'init_values' hashref when some of the fields in your form come from the database and some are process or environment type flags that are not in the database.


Place to store application context for your use in your form's methods.


The form has a 'localizer' object which is shared with form fields. Uses gettext style .po files with names parameters, and is implemented with internal code borrowed from Locale::TextDomain::OO.


validated, is_valid

Flag that indicates if form has been validated. You might want to use this flag if you're doing something in between process and returning, such as setting a stash key. ('is_valid' is a synonym for this flag)

   $form->process( ... );
   $c->stash->{...} = ...;
   return unless $form->validated;


Flag to indicate that validation has been run. This flag will be false when the form is initially loaded and displayed, since validation is not run until MuForm has params to validate.


String to be used as a prefix for field ids and names in an HTML form. Useful for multiple forms on the same HTML page. The prefix is stripped off of the fields before creating the internal field name, and added back in when returning a parameter hash from the 'fif' method. For example, the field name in the HTML form could be "book.borrower", and the field name in the MuForm form (and the database column) would be just "borrower".

   has '+name' => ( default => 'book' );
   has '+field_prefix' => ( default => 'book' );

Also see the Field attribute "prefixed_name", a convenience function which will return the field_prefix + "." + field full_name


This is where args passed to 'process' are set, and the form is filled by params, object, or fields.


Gerda Shank


This software is copyright (c) 2018 by Gerda Shank.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.