https://slides.com/ashish-thakur/di/

Ashish Thakur

@ashish_thakur

About me

@ashish_thakur  | a_thakur

• Procedural php
• The way we did stuff was different from other php frameworks like Laravel, Symfony etc 
• Happy days :)

• Symfony components
• Composer
• php-fig
• Object Oriented PHP
• Dependency Injection

source: http://cdn4.zyxware.com/files/Migrating_your_Drupal_7_themes_to_Drupal_8.jpg

Dependency Injection

Dependency Injection is providing a component with its dependencies either through constructor injection, method calls or the setting of properties.

Before

<?php
namespace Database;

class Database
{
    protected $adapter;

    public function __construct()
    {
        $this->adapter = new MySqlAdapter;
    }
}

class MysqlAdapter {}

After

<?php
namespace Database;

class Database
{
    protected $adapter;

    public function __construct(MySqlAdapter $adapter)
    {
        $this->adapter = $adapter;
    }
}

class MysqlAdapter {}

Depend on Abstactions

<?php
namespace Database;

class Database
{
    protected $adapter;

    public function __construct(AdapterInterface $adapter)
    {
        $this->adapter = $adapter;
    }
}

interface AdapterInterface {}

class MysqlAdapter implements AdapterInterface {}

http://www.phptherightway.com/#dependency_injection

Types of Dependency Injection

Constructor Injection

<?php
namespace Database;

class Database
{
    protected $adapter;

    public function __construct(AdapterInterface $adapter)
    {
        $this->adapter = $adapter;
    }
}

Setter Injection

<?php
namespace Database;

class Database
{
    protected $adapter;

    public function setDatabaseAdapter(AdapterInterface $adapter)
    {
        $this->adapter = $adapter;
    }
}

Property Injection

<?php
namespace Database;

class Database
{
    public $adapter;
}

$adapter = new MysqlAdapter();

$database->adapter = $adapter;

Need for Dependency Injection Container

 $adapter = new MysqlAdapter();

 $database = new Database($adapter);

Symfony

• Better separation of concerns
• Decoupling
• Better unit testability

Resources

• http://www.phptherightway.com/#dependency_injection
• http://fabien.potencier.org/what-is-dependency-injection.html

Thank you

@ashish_thakur | a_thakur | business@srijan.net

https://slides.com/ashish-thakur/di/