OOP Examples

The project provides examples of object-oriented programming (OOP) in Drupal starting from very basic ones. The examples are in sequence: each next example improves the previous one.

Hopefully they would be useful for moving from Drupal 6.7 to Drupal 8. Moreover OOP concepts are not completely new in Drupal. Although Drupal 6,7 does not make thorough use of the native OOP features of PHP, the Drupal code base and API does reflect some principles found in object-oriented programming and design. For example:

• Class definition -> Content Type definition
• Class instance -> Content Type instance
• Namespace -> module_name_*
• Virtual method -> hook_* (like hook_form_alter())
• Event handler method -> hook_* (like hook_cron())

More details are here.

OOP Examples 01 - 03 are applicable to Drupal 7 only, because Drupal 8 has built-in PSR-4 support.

Examples available:

OOP Example 01. Basic classes.
Base class Vehicle and derived classes Car and Motorcycle have been created. Class naming pattern is {module_name}_{class_name}.

OOP Example 02. Basic namespaces.
{module_name} prefix in class naming pattern is no longer needed, because classes are inside a {ModuleName} namespace.

OOP Example 03. PSR-0 Namespaces.
PSR-0 is old Drupal 8 style of module namespaces (under "$module_dir/lib/.."). X Autoload module is required.

OOP Example 04. PSR-4 Namespaces.
PSR-4 is current Drupal 8 style of module namespaces (under "$module_dir/src/.."). See Drupal-8-style PSR-4. X Autoload module >=7.x-5.0 is required for Drupal 7 version.

OOP Example 05. Business logic setup.
Class folders and namespaces structure has been created for further business logic development.

OOP Example 06. Class field $color. Class constructor.
Class field $color has been added for Vehicle class. Default color with translation t() is set up in class constructor because expression is not allowed as field default value. Common method getDescription() has been introduced.

OOP Example 07. Class field $doors.
Class field $doors has been added for Car class. Some car model derived classes (Toyota) have been added.

OOP Example 08. ColorInterface.
Interface ColorInterface has been added. Two different class hierarchies: Vehicle and Fruit implement this interface.

OOP Example 09. More interfaces.
Interfaces DriveInterface and JuiceInterface have been added for class hierarchies Vehicle and Fruit respectively.

OOP Example 10. Interface Inheritance.
Two inherited interfaces have been made. VehicleInterface is a combination of ColorInterface and DriveInterface. FruitInterface is a combination of ColorInterface and JuiceInterface.

OOP Example 11. Dependency injection.
Class Driver has been introduced. Vehicle dependency is provided through a class constructor. The dependency is passed as a DriveInterface, so future implementations of the DriveInterface could be passed as well. For example, Donkey or SpaceShip.

OOP Example 12. Factory.
Factory is an object, which creates another objects. This example provides
a ColorableFactory, which creates classes supporting ColorInterface.