This document discusses how to create a custom field in Drupal 7. It begins by explaining that fields were moved into core in Drupal 7. It then provides steps to create a custom "Collaborator" field with name, role, and link text components. These steps include creating module files, implementing hook functions to define the schema, widget, and formatter. Custom formatters and validation functions are also demonstrated. Documentation resources for fields are shared.

1. FIELDS IN CORE:
HOW TO CREATE A CUSTOM
FIELD
By Ivan Zugec

2. WHO AM I?
• Name: Ivan Zugec
• Drupal username: Ivan Zugec
• Twitter: http://twitter.com/zugec
• Blog: http://zugec.com

3. SESSION AGENDA
• What’s new in Drupal 7
• Understanding fields
• How to create a field
• Custom formatters
• Documentation
• Q&A

4. WHAT’S NEW IN DRUPAL 7

5. WHAT’S NEW IN DRUPAL 7
• InDrupal 6 we used the
CCK module to add fields
into nodes

6. WHAT’S NEW IN DRUPAL 7
• In
Drupal 7 a lot of CCK’s functionality has been moved into
core
• Not all CCK modules made it into core

7. WHAT’S NEW IN DRUPAL 7
• “Node reference” and “User reference” moved to http://
drupal.org/project/references
• “Fieldset” moved to http://drupal.org/project/field_group
• “Contentpermission” moved to http://drupal.org/project/
field_permissions

8. WHAT’S NEW IN DRUPAL 7
• Drupal 7 ships with text, options, number and list
• File and image field all in core

9. UNDERSTANDING FIELDS

10. UNDERSTANDING FIELDS
• Pieceof functionality
attached to an entity (node,
taxonomy, etc...)
• Example: Date module

11. UNDERSTANDING FIELDS
• Fields
have 4 major
components
• Field
• Field type
• Widget
• Formatter

12. UNDERSTANDING FIELDS
• Field
• field.module, field.info and field.install

13. UNDERSTANDING FIELDS
/**
* Implements hook_field_schema().
*/
function text_field_schema($field) {
switch ($field['type']) {
case 'text':
$columns = array(
'value' => array(
'type' => 'varchar',
• Field type 'length' => $field['settings']['max_length'],
'not null' => FALSE,
),
);
break;
• How the field will be stored
case 'text_long':
....
in the database
break;
}
$columns += array(
'format' => array(
'type' => 'varchar',
'length' => 255,
• Using hook_field_schema ),
'not null' => FALSE,
);
return array(
'columns' => $columns,
• Using hook_field_info 'indexes' => array(
),
'format' => array('format'),
'foreign keys' => array(
'format' => array(
'table' => 'filter_format',
'columns' => array('format' => 'format'),
),
),
);

14. UNDERSTANDING FIELDS
• Widget
• Form element a user will use
to enter in the data

15. UNDERSTANDING FIELDS

16. UNDERSTANDING FIELDS
• Formatter
• How to data will be
displayed

17. HOW TO CREATE A FIELD

18. HOW TO CREATE A FIELD
• Createa custom
“Collaborators” field
• Module will be called
“collabfield”
• Unlimited value field with a
Name, Role and Link text
fields within

19. HOW TO CREATE A FIELD
• Createa module called
collabfield
• Createcollabfield.info,
collabfield.install and
collabfield.module files

20. HOW TO CREATE A FIELD
collabfield.info
; $Id$
name = Collaborator field
description = Custom collaborator field.
dependencies[] = field_ui
core = 7.x

21. HOW TO CREATE A FIELD
collabfield.install
<?php
// $Id$
/**
* Implements hook_install().
*/
function collabfield_install() {
}
/**
* Implements hook_uninstall().
*/
function collabfield_uninstall() {
}

22. HOW TO CREATE A FIELD
/**
collabfield.install
* Implementation of hook_field_schema().
*/
function collabfield_field_schema($field) {
if ($field['type'] == 'collabfield') {
$schema['columns']['name'] = array(
'type' => 'varchar',
'length' => '255',
'not null' => FALSE,
);
$schema['columns']['role'] = array(
'type' => 'varchar',
'length' => '255',
'not null' => FALSE,
);
$schema['columns']['link'] = array(
'type' => 'varchar',
'length' => '255',
'not null' => FALSE,
);
$schema['indexes'] = array(
'name' => array('name'),
'role' => array('role'),
'link' => array('link'),
);
return $schema;
}

23. HOW TO CREATE A FIELD
collabfield.module
<?php
// $Id$
/**
* Implementation of hook_field_info().
*/
function collabfield_field_info() {
return array(
'collabfield' => array(
'label' => t('Collaborator'),
'description' => t('Custom collaborators field.'),
'default_widget' => 'collabfield_collabfield_form',
'default_formatter' => 'collabfield_default',
),
);
}

24. HOW TO CREATE A FIELD
collabfield.module
/**
* Implementation of hook_field_is_empty().
*/
function collabfield_field_is_empty($item, $field) {
if ($field['type'] == 'collabfield') {
if (empty($item['name']) && empty($item['role']) && empty($item['link'])) {
return TRUE;
}
}
return FALSE;
}

25. HOW TO CREATE A FIELD
• Create a widget
• Use hook_field_widget_info
to setup field
• Use
hook_field_widget_form for
the actual form element

26. HOW TO CREATE A FIELD
/**
* Implements hook_field_widget_info().
*/
function collabfield_field_widget_info() {
return array(
'collabfield_collabfield_form' => array(
'label' => t('Collabfield form'),
'field types' => array('collabfield'),
'behaviors' => array(
'multiple values' => FIELD_BEHAVIOR_DEFAULT,
//Use FIELD_BEHAVIOR_NONE for no default value.
'default value' => FIELD_BEHAVIOR_DEFAULT,
),
),
);
}

27. HOW TO CREATE A FIELD
/**
* Implementation of hook_field_widget_form().
*/
function collabfield_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
$base = $element;
if ($instance['widget']['type'] == 'collabfield_collabfield_form') {
$widget = $instance['widget'];
$settings = $widget['settings'];
$element['name'] = array(
'#type' => 'textfield',
'#title' => t('Name'),
'#default_value' => isset($items[$delta]['name']) ? $items[$delta]['name'] : NULL,
);
$element['role'] = array(
'#type' => 'textfield',
'#title' => t('Role'),
'#default_value' => isset($items[$delta]['role']) ? $items[$delta]['role'] : NULL,
);
$element['link'] = array(
'#type' => 'textfield',
'#title' => t('Link'),
'#default_value' => isset($items[$delta]['link']) ? $items[$delta]['link'] : NULL,
'#element_validate' => array('_collabfield_link_validate'),
);
}
return $element;
}

28. HOW TO CREATE A FIELD
• To validate an element add #element_validate to the specific
element
$element['link'] = array(
'#type' => 'textfield',
'#title' => t('Link'),
'#default_value' => isset($items[$delta]['link']) ? $items[$delta]['link'] : NULL,
'#element_validate' => array('_collabfield_link_validate'),
);
/**
* Validation callback for a collabfield link element.
*/
function _collabfield_link_validate($element, &$form_state, $form) {
$value = $element['#value'];
if (!empty($value) && !valid_url($value, TRUE)) {
form_error($element, t('Invalid URL.'));
}
}

29. HOW TO CREATE A FIELD
• Drupalships with three form element validators in
field.module
• _element_validate_integer()
• _element_validate_integer_positive()
• _element_validate_number()

30. HOW TO CREATE A FIELD
• Create a formatter
• Use
hook_field_formatter_info
to setup a formatter
• Use
hook_field_formatter_view
for the actual formatter

31. HOW TO CREATE A FIELD
/**
* Implements hook_field_formatter_info().
*/
function collabfield_field_formatter_info() {
return array(
'collabfield_default' => array(
'label' => t('Default'),
'field types' => array('collabfield'),
),
);
}

32. HOW TO CREATE A FIELD
/**
* Implements hook_field_formatter_view().
*/
function collabfield_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
$element = array();
switch ($display['type']) {
case 'collabfield_default':
foreach ($items as $delta => $item) {
$element[$delta]['#markup'] = theme('collabfield_formatter_default', $item);
}
break;
}
return $element;
}

33. CUSTOM FORMATTERS

34. CUSTOM FORMATTERS
• Formatter to change default term reference link formatter
• Create as custom module
• Change URL taxonomy/term/[tid] to whatever/[tid]

35. CUSTOM FORMATTERS
/**
* Implements hook_field_formatter_info().
*/
function termpathfield_field_formatter_info() {
return array(
'termpathfield_term_reference_link' => array(
'label' => t('Custom path link'),
'field types' => array('taxonomy_term_reference'),
'settings' => array(
'taxonomy_custom_url' => 'taxonomy/term/[tid]',
),
),
);
}

36. CUSTOM FORMATTERS
/**
* Implements hook_field_formatter_settings_form().
*/
function termpathfield_field_formatter_settings_form($field, $instance, $view_mode, $form, &$form_state) {
$display = $instance['display'][$view_mode];
$settings = $display['settings'];
$form = array();
if ($display['type'] == 'termpathfield_term_reference_link') {
$form['taxonomy_custom_url'] = array(
'#type' => 'textfield',
'#title' => t('Custom term page URL'),
'#default_value' => $settings['taxonomy_custom_url'],
'#required' => TRUE,
);
}
return $form;
}

37. CUSTOM FORMATTERS

38. CUSTOM FORMATTERS
/**
* Implements hook_field_formatter_settings_summary().
*/
function termpathfield_field_formatter_settings_summary($field, $instance, $view_mode) {
$display = $instance['display'][$view_mode];
$settings = $display['settings'];
$summary = '';
if ($display['type'] == 'termpathfield_term_reference_link') {
$summary = $settings['taxonomy_custom_url'];
}
return $summary;
}

39. CUSTOM FORMATTERS

40. CUSTOM FORMATTERS
/**
* Implements hook_field_formatter_view().
*/
function termpathfield_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
$result = array();
switch ($display['type']) {
case 'termpathfield_term_reference_link':
foreach ($items as $delta => $item) {
$term = taxonomy_term_load($item['tid']);
$uri_path = str_replace('[tid]', $term->tid, $display['settings']['taxonomy_custom_url']);
$uri = url($uri_path, array('absolute' => TRUE));
$result[$delta] = array(
'#type' => 'link',
'#title' => $term->name,
'#href' => $uri,
);
}
break;
}
return $result;
}

41. DOCUMENTATION

42. DOCUMENTATION
• http://api.drupal.org
• Field Types API
http://api.drupal.org/api/
drupal/modules--field--
field.api.php/group/
field_types/7

43. DOCUMENTATION
• Other core field modules
• list.module, number.module,
options.module and
text.module
• modules/fields/modules

44. DOCUMENTATION
• Examples for Developers
• http://drupal.org/project/
examples

45. THE END

46. Q&A