Using Value Objects for Dependency Injection

README.md

This is an example of how to use Value Objects for dependency injection, as a response to a blog post by Tom McFarlin:

What’s Too Much For Passing Data via Dependency Injection?

bootstrap.php

<?php

$plugin = new Plugin( new PluginRoot( __FILE__ ) );

Plugin.php

<?php

class Plugin
{
  protected $plugin_root;

  private $loaded;

  public function __construct(PluginRoot $plugin_root)
  {
    $this->loaded      = false;
    $this->plugin_root = $plugin_root;
  }

  public function isLoaded()
  {
    return $this->loaded;
  }

  public function load()
  {
    // ...
  }

  public function getSubscribers()
  {
    return [
      new OtherPluginClass($this->plugin_root)
    ];
  }
}

PluginRoot.php

<?php

class PluginRoot {
  
  protected $file;

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

  public function get_path() {
    return plugin_dir_path( $this->file );
  }
  
  public function get_url() {
    return plugin_dir_url( $this->file );
  }
}