NAME

Form::Model -- default model base class

SYNOPSIS

    # A class to define a form in your application
    package MyApplication::Form::User;
    use strict;

    # Inherit from the form model class for your ORM
    use base 'Form::Processor::Model::CDBI

    # Relate the form to a specific ORM class
    sub object_class{ 'MyDB::User' }

    sub profile {

        [...]
    }

DESCRIPTION

This is an empty base class that defines methods called by Form::Processor to support interfacing forms with a data store such as a database.

This module provides instructions on methods to override to create a Form::Processor::Model class to work with a specific object relational mapping (ORM) tool.

For an example see Form::Processor::Model::CDBI for working with the Class::DBI ORM.

METHODS

object_class

This sets and returns a value used by the model class to access the ORM class related to a form.

For example, if the model class interfaces with Class::DBI and a form is created for updating, say, MyDB::Users then in your form class:

    sub object_class { 'MyDB::Users' }

This gives the model class a way to access the data store. If this is not a fixed value (as above) then do not define the method in your subclass and instead set the value when the form is created:

    my $form = MyApp::Form::Users->new;
    $form->object_class( $my_object );

The value can be any scalar (or object) needed by the specific ORM to access the data related to the form.

This method does not need to be defined in a model subclass unless you wish to do extra validation.

The default returns the class of "item", if item is defined. It's not as useful as it sounds because "item" doesn't exist when creating new records.

This can also be set as a parameter to new, but will be overridden in subclasses.

init_item

This is called first time $form->item is called. This method must be defined in the model class to fetch the object based on the item id. It should return the item's object. Column values are fetched and updated by calling methods on the returned object.

For example, with Class::DBI you might return:

    return $self->object_class->retrieve( $self->item_id );

guess_field_type

Returns the guessed field type. The field name is passed as the first argument. This is only required if using "Auto" type of fields in your form classes.

The default is to die, since we can't guess. To be useful this must be overridden in a form model class. You could override this in your form class, for example, if you use a field naming convention that indicates the field type.

Form::Processor::Model::CDBI uses CDBI's meta_info() method to look at relationships and figure out the field type. Other form model classes might look at the database for this information, for example.

lookup_options

This method is called to find possible options for a given field from the database. The default method returns undef.

Returns an array reference of key/value pairs for the column passed in. These values are used for the values and labels for field types that provide a list of options to select from (e.g. Select, Multiple).

A 'Select' type field (or a field that inherits from Form::Processor::Field::Select) can set a number of scalars that control how options are looked up:

    label_column()          - the name of the column that holds the label
    active_column()         - column name that indicates if a row is acitve
    sort_order()            - column name used for sorting the options

The default for label_column is "name".

Form::Processor::Model::CDBI, for example, uses meta_info() to look at related classes and returns a list of options sorted by the label column which by default is "name".

init_value

This method populates a form field's value from the item object. This is typically done by calling the field's name as an method on the object.

The default method basically does:

    my $name = $field->name;
    return $item->can( $name ) ? $item->$name : undef
        if blessed( $item );

update_from_form

Update or create the object.

This needs to be overridden in the model subclass or in your form subclass.

It should update $form->item, if set, otherwise create a new item.

The update/create should be done inside a transaction if do_transaction is available.

Any field names that are related to the class by "has_many" and have a mapping table should also be updated.

Validation must also be run unless validation has already been run. ($form->clear might need to be called if the $form object stays in memory between requests.)

See Form::Processor::Model::CDBI for an example.

The default method dies.

model_validate

Validates profile items that are dependent on the model. This is called via the validation process and the model class must at least validate "unique" constraints defined in the form class.

Any errors on a field found should be set by calling the field's add_error method:

    $field->add_error('Value must be unique in the database');

The default method does nothing.

AUTHOR

Bill Moseley

LICENSE

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