Synapse India Reviews on Entities in Drupal 7

& the Entity API

About Me

Founder & Chief Solutions Architect@ Modern Biz Consulting in Oakland

Strong development background Working with Drupal since 2006 Developer, architect, project manager Focus on complex web application development

Agenda

Ways we represent data in D6 vs D7 Entities, entity types, & bundles Fields (formerly CCK) The Entity API contrib module How (and why) to define a custom entity Using EntityFieldQuery Defining entity property info Leveraging the Entity Metadata Wrapper

Poll

Who here is...

– Brand new to Drupal?

– A site builder?

– A module developer?

– On the business side of things? Who here has...

– Created a custom D7 entity?

– Not created a custom D7 entity?

D6 Data

(Custom database table) User Comment File Taxonomy vocabulary Taxonomy term Node

– Page, Blog post, (custom content type)

D7 Data

(Custom database table) Entity

– User

– Comment

– File

– Taxonomy vocabulary

– Taxonomy term

– Node• Page, Blog post, (custom content type)

(Custom entity type)

Entity Types

Elemental building block for most important data in Drupal 7

Represents a concept or noun Different types store different data

– Generally in a single DB table

– Eg: Node• Title, body, created timestamp, etc.

– Eg: User• Username, created timestamp, last visit timestamp, etc.

Defined using hook_entity_info()

Entity

Instance of an entity type Examples of entities from core:

– The user jdleonard with uid 80902

– The page “Drupal Rocks” with nid 44 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 convenience wrappers• Eg: node_load() and user_load()

Entity Bundles

Subtype of an entity Eg: Page and Blog post

– Two content types (bundles) of node entity type Not all entity types have more than one bundle

– Eg: User• No subtypes; concept stands on its own

Why We Need Entity Bundles

Each entity type stores some data in a table

– We call these pieces of data “properties”

– Eg: node• Title, body, author (uid), created timestamp

• But not all nodes are created equal– Page may have data beyond that captured by node– Blog posts get tagged– We need fields!

CCK: Content Construction Kit (D6)

Contrib module Store additional data per content (node) content type Eg: Fivestar

– Contrib module leveraging contrib CCK API

– Allows nodes to be rated (think 1-5 stars)

– Eg: let users rate pages or blog posts

Fields (D7)

Core concept Store additional data per entity type Applies power of CCK to all entity types

– Not just nodes! Eg: Fivestar

– Contrib module leveraging core Field API

– Allows entities to be rated

– Eg: let users rate pages, blog posts, users, comments, custom entities

Entities in Core vs Contrib

Entities are a Drupal 7 core concept Core provides the “Entity API”

– Functions and hooks to define and interact with entities, entity types, and entity bundles

Everything we've discussed so far is part of Drupal 7 core (no contrib modules necessary)

Not everything “made it into” D7 core

– Thankfully there's the “Entity API” contrib module• (confusingly named)

Entity API Contrib Module

Makes dealing with entities easier Provides full CRUD functionality

– CReate, Update, and Delete Allows definition of metadata about entities Optionally makes entity data

– Exportable (for configuration)

– Revisionable (eg: node revisions) Optional administrative UI for managing entities Object-oriented representation of entity types

Core or contrib Entity API?

Documentation for core's Entity API is separate from that for the Entity API contrib module

In practice, you'll probably always use the Entity API contrib module

– It provides so much awesome functionality! Don't get confused

– Always install the Entity API contrib module when defining an entity

– Make sure to read the contrib module's documentation

Contrib Modules Defining Entities

Commerce

– Commerce Product, Commerce Payment Transaction Organic Groups

– OG Membership, OG Membership Type Rules

– Rules Configuration Message (think activity stream)

– Message, Message Type, Message Type Category … and many more!

Example Custom Entity Type

TextbookMadness.com

– Classified listings for textbooks at schools

– Online price comparison shopping (prices from Amazon, Textbooks.com, etc.)

Online prices are

– Fetched from a third-party API and stored by Drupal

– Hereafter known as Offers

How Shall we Define an Offer?

We could use the UI to define an offer node with a bunch of fields to store pricing information

But there's a lot of overhead!

– Don't need/want a page (path) per offer

– Don't need/want revisions

– Don't need/want node base table information• Language (and translation info), Title, Author,

Published status, Created date, Commenting, Promoting, etc.

– Don't need/want UI for adding, editing, etc. We want an entity!

Implement hook_schema()

$schema['tbm_offer'] = array( // SIMPLIFIED FOR SLIDE

'fields' => array(

'offer_id' => array('type' => 'serial'),

'isbn' => array('type' => 'int'),

'retailer_id' => array('type' => 'int'),

'price' => array('type' => 'int'),

'last_updated' => array('type' => 'int'),

),

'primary key' => array('offer_id')

);

Implement hook_entity_info()$entities['tbm_offer'] = array(

'label' => t('Offer'),

'plural label' => t('Offers'),

'entity class' => 'Entity',

'controller class' => 'EntityAPIController',

'module' => 'tbm',

'base table' => 'tbm_offer',

'fieldable' => FALSE,

'entity keys' => array(

'id' => 'offer_id',

));

Make an Entity Type Exportable$entities['tbm_offer'] = array(

'label' => t('Offer'),

'plural label' => t('Offers'),

'entity class' => 'Entity',

'controller class' => 'EntityAPIControllerExportable',

'module' => 'tbm',

'base table' => 'tbm_offer',

'fieldable' => FALSE, 'exportable' => TRUE,

'entity keys' => array(

'id' => 'offer_id', 'name' => 'my_machine_name'

));

Make an Entity Type Revisionable$entities['tbm_offer'] = array(

'label' => t('Offer'),

'plural label' => t('Offers'),

'entity class' => 'Entity',

'controller class' => 'EntityAPIController',

'module' => 'tbm',

'base table' => 'tbm_offer', 'revision_table' => 'tbm_o_revision',

'fieldable' => FALSE,

'entity keys' => array(

'id' => 'offer_id', 'revision' => 'revision_id',

));

Other hook_entity_info() configuration$entities['tbm_offer'] = array( …

'entity class' => 'TbmOfferEntity', // Extends Entity class

'controller class' => 'TbmOfferEntityController',

'access callback' => 'tbm_offer_access',

'admin ui' => array(

'path' => 'admin/structure/offers',

'file' => 'tbm.admin.inc',

),

'label callback' => 'entity_class_label',

'uri callback' => 'entity_class_uri',

); // TbmOfferEntity->defaultLabel(), defaultUri()

Entity Property Info

hook_entity_property_info()

– Defines entity metadata

– Provided for core entities Enables all kinds of great functionality in modules

that leverage the Entity API contrib module

– Examples coming later

Entity Property Info

Automatically generated from hook_schema()

– Doesn't understand foreign key relationships (references)

– Doesn't know when an integer is actually a date (eg: unix timestamps)

We can fill in the gaps with hook_entity_property_info_alter()