Facade en PHP
Facade es un patrón de diseño estructural que proporciona una interfaz simplificada (pero limitada) a un sistema complejo de clases, bibliotecas o _frameworks_.
El patrón Facade disminuye la complejidad general de la aplicación, al mismo tiempo que ayuda a mover dependencias no deseadas a un solo lugar.
Complejidad:
Popularidad:
Ejemplos de uso: El patrón Facade se utiliza habitualmente en aplicaciones PHP, donde las clases fachada simplifican el trabajo con bibliotecas o API complejas.
Identificación: El patrón Facade se puede reconocer en una clase con una interfaz simple, pero que delega la mayor parte del trabajo a otras clases. Normalmente, las fachadas gestionan todo el ciclo de vida de los objetos que utilizan.
Ejemplo conceptual
Este ejemplo ilustra la estructura del patrón de diseño Facade y se centra en las siguientes preguntas:
- ¿De qué clases se compone?
- ¿Qué papeles juegan esas clases?
- ¿De qué forma se relacionan los elementos del patrón?
Después de conocer la estructura del patrón, será más fácil comprender el siguiente ejemplo basado en un caso de uso real de PHP.
index.php: Ejemplo conceptual
<?php
namespace RefactoringGuru\Facade\Conceptual;
/**
* The Facade class provides a simple interface to the complex logic of one or
* several subsystems. The Facade delegates the client requests to the
* appropriate objects within the subsystem. The Facade is also responsible for
* managing their lifecycle. All of this shields the client from the undesired
* complexity of the subsystem.
*/
class Facade
{
protected $subsystem1;
protected $subsystem2;
/**
* Depending on your application's needs, you can provide the Facade with
* existing subsystem objects or force the Facade to create them on its own.
*/
public function __construct(
Subsystem1 $subsystem1 = null,
Subsystem2 $subsystem2 = null
) {
$this->subsystem1 = $subsystem1 ?: new Subsystem1();
$this->subsystem2 = $subsystem2 ?: new Subsystem2();
}
/**
* The Facade's methods are convenient shortcuts to the sophisticated
* functionality of the subsystems. However, clients get only to a fraction
* of a subsystem's capabilities.
*/
public function operation(): string
{
$result = "Facade initializes subsystems:\n";
$result .= $this->subsystem1->operation1();
$result .= $this->subsystem2->operation1();
$result .= "Facade orders subsystems to perform the action:\n";
$result .= $this->subsystem1->operationN();
$result .= $this->subsystem2->operationZ();
return $result;
}
}
/**
* The Subsystem can accept requests either from the facade or client directly.
* In any case, to the Subsystem, the Facade is yet another client, and it's not
* a part of the Subsystem.
*/
class Subsystem1
{
public function operation1(): string
{
return "Subsystem1: Ready!\n";
}
// ...
public function operationN(): string
{
return "Subsystem1: Go!\n";
}
}
/**
* Some facades can work with multiple subsystems at the same time.
*/
class Subsystem2
{
public function operation1(): string
{
return "Subsystem2: Get ready!\n";
}
// ...
public function operationZ(): string
{
return "Subsystem2: Fire!\n";
}
}
/**
* The client code works with complex subsystems through a simple interface
* provided by the Facade. When a facade manages the lifecycle of the subsystem,
* the client might not even know about the existence of the subsystem. This
* approach lets you keep the complexity under control.
*/
function clientCode(Facade $facade)
{
// ...
echo $facade->operation();
// ...
}
/**
* The client code may have some of the subsystem's objects already created. In
* this case, it might be worthwhile to initialize the Facade with these objects
* instead of letting the Facade create new instances.
*/
$subsystem1 = new Subsystem1();
$subsystem2 = new Subsystem2();
$facade = new Facade($subsystem1, $subsystem2);
clientCode($facade);
Output.txt: Resultado de la ejecución
Facade initializes subsystems:
Subsystem1: Ready!
Subsystem2: Get ready!
Facade orders subsystems to perform the action:
Subsystem1: Go!
Subsystem2: Fire!
Ejemplo del mundo real
Piensa en el patrón Facade como un adaptador de simplicidad para algunos subsistemas complejos. El patrón Facade aísla la complejidad dentro de una única clase y permite al código de otras aplicaciones utilizar la interfaz directa.
En este ejemplo, el patrón Facade esconde al código cliente la complejidad de la API de YouTube y la biblioteca de FFmpeg. En lugar de trabajar con decenas de clases, el cliente utiliza un método simple en la fachada.
index.php: Ejemplo del mundo real
<?php
namespace RefactoringGuru\Facade\RealWorld;
/**
* The Facade provides a single method for downloading videos from YouTube. This
* method hides all the complexity of the PHP network layer, YouTube API and the
* video conversion library (FFmpeg).
*/
class YouTubeDownloader
{
protected $youtube;
protected $ffmpeg;
/**
* It is handy when the Facade can manage the lifecycle of the subsystem it
* uses.
*/
public function __construct(string $youtubeApiKey)
{
$this->youtube = new YouTube($youtubeApiKey);
$this->ffmpeg = new FFMpeg();
}
/**
* The Facade provides a simple method for downloading video and encoding it
* to a target format (for the sake of simplicity, the real-world code is
* commented-out).
*/
public function downloadVideo(string $url): void
{
echo "Fetching video metadata from youtube...\n";
// $title = $this->youtube->fetchVideo($url)->getTitle();
echo "Saving video file to a temporary file...\n";
// $this->youtube->saveAs($url, "video.mpg");
echo "Processing source video...\n";
// $video = $this->ffmpeg->open('video.mpg');
echo "Normalizing and resizing the video to smaller dimensions...\n";
// $video
// ->filters()
// ->resize(new FFMpeg\Coordinate\Dimension(320, 240))
// ->synchronize();
echo "Capturing preview image...\n";
// $video
// ->frame(FFMpeg\Coordinate\TimeCode::fromSeconds(10))
// ->save($title . 'frame.jpg');
echo "Saving video in target formats...\n";
// $video
// ->save(new FFMpeg\Format\Video\X264(), $title . '.mp4')
// ->save(new FFMpeg\Format\Video\WMV(), $title . '.wmv')
// ->save(new FFMpeg\Format\Video\WebM(), $title . '.webm');
echo "Done!\n";
}
}
/**
* The YouTube API subsystem.
*/
class YouTube
{
public function fetchVideo(): string { /* ... */ }
public function saveAs(string $path): void { /* ... */ }
// ...more methods and classes...
}
/**
* The FFmpeg subsystem (a complex video/audio conversion library).
*/
class FFMpeg
{
public static function create(): FFMpeg { /* ... */ }
public function open(string $video): void { /* ... */ }
// ...more methods and classes... RU: ...дополнительные методы и классы...
}
class FFMpegVideo
{
public function filters(): self { /* ... */ }
public function resize(): self { /* ... */ }
public function synchronize(): self { /* ... */ }
public function frame(): self { /* ... */ }
public function save(string $path): self { /* ... */ }
// ...more methods and classes... RU: ...дополнительные методы и классы...
}
/**
* The client code does not depend on any subsystem's classes. Any changes
* inside the subsystem's code won't affect the client code. You will only need
* to update the Facade.
*/
function clientCode(YouTubeDownloader $facade)
{
// ...
$facade->downloadVideo("https://www.youtube.com/watch?v=QH2-TGUlwu4");
// ...
}
$facade = new YouTubeDownloader("APIKEY-XXXXXXXXX");
clientCode($facade);
Output.txt: Resultado de la ejecución
Fetching video metadata from youtube...
Saving video file to a temporary file...
Processing source video...
Normalizing and resizing the video to smaller dimensions...
Capturing preview image...
Saving video in target formats...
Done!
