The document discusses Drupal 7's concept of entities, explaining how data is represented in a new way compared to Drupal 6. It highlights the differences between entities and nodes, the role of the Entity API, and includes a live example through the website textbookmadness.com, which utilizes these concepts for managing textbook listings. Additionally, it covers the definitions and functionalities of various entity types and their schema implementations.

1. Drupal 7 Entities
{ Entities, nodes, fields, the Entity API &
TextbookMadness.com
{ JD Leonard
Freelance Drupal Consultant & Developer
Founder, TextbookMadness.com { Berkeley DUG 2/27/12

2. Entities, Entities, Entities
Powerful new concept in Drupal 7
 Agenda:
 How data is represented
 Drupal 6 vs. Drupal 7
 Entities
 Fields (CCK)
 Entities vs. nodes
 The Entity API (contrib module)
 Live example: entities, nodes, and fields used
to build TextbookMadness.com

3. { Drupal 6 { Drupal 7
 {Custom DB table}  {Custom DB table]
 User  Entity
 Comment  User
 Comment
 Taxonomy
 Taxonomy
 Node
 Node
 Page  Page
 Blog post  Blog post
 {Custom node type}  {Custom node type}
 {Custom entity type}
Drupal Data

4. Entity Types
 Elemental building block for most data in Drupal 7
 Represents a concept or noun
 In core: user, comment, taxonomy, & node
 Stores data differently
 Generally in a single DB table
 Node
 Title, body, created timestamp
 User
 Username, created timestamp, last visit timestamp
 Defined using hook_entity_info() – example later!

5. Entity
 Instance of an entity type
 In core:
 Users, comments, taxonomies, and nodes are entities
 Eg: the user jdl1234 with uid 12 is an entity
 Eg: the page ‚Drupal rocks‛ with nid 44 is an entity
 Any entity can be loaded with entity_load()
 Eg: entity_load(‘node’, array(44, 65))
 Returns an array with two nodes with nids 44 and 65
 Core provides some wrappers that do extra work
 Eg: node_load() and user_load()

6. Entity Bundles
 Bundle
 Subtype of an entity
 Eg: page & blog post
 Two content types of node entity type
 ‚Bundles‛ of node entity type
 Not all entity types have more than one
 Eg: user
 Concept stands on its own
 Why bother?
 Each entity type stores some data in a table
 Eg: node
 Title, body, created timestamp
 But not all nodes are created equal
 Page may have data beyond that captured by node
 Blog posts get tagged

7. CCK, Fields, & Entities
 Drupal 6 CCK (Content Construction Kit)
 Contrib module
 Store additional data per content (node) type
 Eg: Fivestar
 Contrib module leveraging contrib CCK API
 Allows nodes to be rated (think 1-5 stars)
 Eg: let users rate pages
 Drupal 7 fields
 Core concept
 Store additional data per entity type
 Applies power of CCK to all entity types
 Eg: Fivestar
 Contrib module leveraging core Field API
 Allows entities to be rated
 Eg: let users rate pages, users, comments, custom entities

8. Entities & Nodes
 Similarities
 Represent ‚things‛; store data
 Fieldable
 Types can be defined in code

9. { Nodes { Entities
 Site building  Optionally fieldable
 UI to add/edit  Development
content types, fields,  Lightweight
and content  No UI provided
 Versioning built in  Data storage up to
 Data stored in nodes you
table and fields  Can be more
performant/scalable
Entities vs. Nodes

10. Core Entities & Entity API
 Entities are a Drupal 7 core concept
 Core functions and hooks provided to interact with
entities and entity types
 EntityFieldQuery
 Core API for querying entities
 Can query entity data (‚properties‛) and field data
 Can query field data across entity types
 Eg: ‚return all pages and users tagged with taxonomy
term 456‛
 Returns entity IDs
 Usually you’ll then load with entity_load()
 The Entity API contrib module builds on core

11. Entity API
 Makes dealing with entities easier
 Provides full CRUD functionality
 CReate, Update, and Delete
 Allows definition of metadata about entities and
relationships between them
 Views integration
 Rules integration
 Search API integration
 Optionally make data exportable
 Optional administrative UI for managing entities
 Object-oriented representation of entity types
 Enables extending an entity type’s functionality

12. Modules Using Entity API
 Profile2
 Organic Groups
 Rules
 Message
 Drupal commerce
 < and lots more!

13. TextbookMadness.com
 Drupal 7 site
 Cross between Craigslist and Kayak
 Free textbook classified listings
 Private to each college we partner with
 Helps students buy and sell used books with each other
 Online price comparison
 Prices from 30+ online retailers
 Amazon, Half, Chegg, Textbooks.com, you name it
 New, used, rental, international edition, eBook, and
buyback prices
 Uses entities and the Entity API
 Demo!

14. Textbook Madness Data
 Users (John Smith)
 Schools (Rice University)
 Retailers (Amazon.com
 Textbooks (with an ISBN)
 Offers (online prices)
 Listings (student book classifieds)
 Everything above except users are defined as custom
entity types

15. School Entity Definition
/* Implements hook_entity_info(). // Drupal core hook */
function tbm_entity_info() {
$entities = array(
'tbm_school' => array( // Machine name for my entity
'label' => t('School'),
'plural label' => t('Schools'),
'entity class' => 'TbmSchoolEntity', // Advanced. You can put ‘Entity’
'controller class' => 'TbmSchoolEntityController', // Advanced. You can put ‘EntityAPIController’
'base table' => 'tbm_school', // Name of the related table defined in hook_schema() in tbm.install
'fieldable' => FALSE,
'entity keys' => array(
'id' => 'school_id', // Primary key as defined in hook_schema()
'label' => 'name', // Column in hook_schema() to be used to represent the entity in a friendly way
),
'uri callback' => 'entity_class_uri',
'access callback' => 'tbm_school_access', // Callback defined to return TRUE if the school is enabled
'module' => 'tbm', // My module name
'admin ui' => array(
'path' => 'admin/structure/schools',
'file' => 'tbm.admin.inc', // Where tbm_school_form() for add/edit form is defined
'file path' => drupal_get_path('module', 'tbm') . '/pages',
),
),
);
return $entities;
}

16. School Schema Definition
/* Implements hook_schema(). */
function tbm_schema() {
$schema['tbm_school'] = array(
'fields' => array(
'school_id' => array('type' => 'serial', 'size' => 'small', 'unsigned' => TRUE, 'not null' => TRUE),
'machine_name' => array('type' => 'varchar', 'length' => 100, 'not null' => TRUE, 'description' => 'The machine name of the school.'),
'name' => array('type' => 'varchar', 'length' => 128, 'not null' => TRUE, 'description' => 'The name of the school.'),
'name_short' => array('type' => 'varchar', 'length' => 64, 'description' => 'The short name of the school.'),
'name_long' => array('type' => 'varchar', 'length' => 255, 'description' => 'The long name of the school.'),
'url' => array('type' => 'varchar', 'length' => 1024, 'not null' => TRUE, 'description' => 'The URL of the school's homepage.'),
'email_domains' => array('type' => 'varchar', 'length' => 1024, 'description' => 'The email domains (comma delimited) valid for the school.'),
'sponsor1_name' => array('type' => 'varchar', 'length' => 64, 'description' => 'The name of the first sponsor.'),
'sponsor1_name_short' => array('type' => 'varchar', 'length' => 32, 'description' => 'The short name of the first sponsor.'),
'sponsor1_name_long' => array('type' => 'varchar', 'length' => 128, 'description' => 'The long name of the first sponsor.'),
'sponsor1_url' => array('type' => 'varchar', 'length' => 1024, 'description' => 'The URL of the first sponsor's homepage.'),
'sponsor2_name' => array('type' => 'varchar', 'length' => 64, 'description' => 'The name of the second sponsor.'),
'sponsor2_name_short' => array('type' => 'varchar', 'length' => 32, 'description' => 'The short name of the second sponsor.'),
'sponsor2_name_long' => array('type' => 'varchar', 'length' => 128, 'description' => 'The long name of the second sponsor.'),
'sponsor2_url' => array('type' => 'varchar', 'length' => 1024, 'description' => 'The URL of the second sponsor's homepage.'),
'enabled' => array('type' => 'int', 'size' => 'tiny', 'unsigned' => TRUE, 'not null' => TRUE, 'description' => 'Whether the school is enabled.'),
'listed' => array('type' => 'int', 'size' => 'tiny', 'unsigned' => TRUE, 'not null' => TRUE, 'description' => 'Whether the school is listed.'),
),
'primary key' => array('school_id'),
'unique keys' => array(
'machine_name' => array('machine_name'),
),
);
return $schema;

17. School EntityFieldQuery
 This function shows how to use an EntityFieldQuery
 Users are necessarily associated with a school
 I have a field, field_school, attached to the user entity type, which
stores this relationship data
 The query finds active users (status == 1) at the given school
/**
* Load an array of uids of users at the school with the given ID.
* @param int $school_id The ID of the school to load users for
*/
function tbm_school_uids($school_id) {
$query = new EntityFieldQuery();
$result = $query
->entityCondition('entity_type', 'user')
->propertyCondition('status', 1)
->fieldCondition('field_school', 'school_id', $school_id)
->execute();
return array_key_exists('user', $result) ? array_keys($result['user']) : array();
}

18. The end!