Facade Pattern

The primary goal of a Facade Pattern is not to avoid you having to read the manual of a complex API. It's only a side-effect. The first goal is to reduce coupling and follow the Law of Demeter.

A Facade is meant to decouple a client and a sub-system by embedding many (but sometimes just one) interface, and of course to reduce complexity.

A facade does not forbid you the access to the sub-system

You can (you should) have multiple facades for one sub-system

That's why a good facade has no new in it. If there are multiple creations for each method, it is not a Facade, it's a Builder or a [Abstract|Static|Simple] Factory [Method].

The best facade has no new and a constructor with interface-type-hinted parameters. If you need creation of new instances, use a Factory as argument.

The above may sound complicated but essentially all a Facade is doing is grouping code together so if you need to call it, it's simple and easier to understand whats going on, i.e:

Adding this to code:

$this->eatBreakfast();

Beats this (this would be encapsulated inside eatBreakfast()):

$this->openFridge();
$this->getSausages();
$this->getEggs();
$this->getBacon();
$this->cook();
$this->openMouth();
$this->swallow();

Bios

namespace DesignPatterns\Structural\Facade;

interface Bios
{
    public function execute();
    public function waitForKeyPress();
    public function launch(OperatingSystem $os);
    public function powerDown();
}

Operating System

namespace DesignPatterns\Structural\Facade;

interface OperatingSystem
{
    public function halt();

    public function getName(): string;
}

Facade

namespace DesignPatterns\Structural\Facade;

class Facade
{
    public function __construct(private Bios $bios, private OperatingSystem $os)
    {
    }

    public function turnOn()
    {
        $this->bios->execute();
        $this->bios->waitForKeyPress();
        $this->bios->launch($this->os);
    }

    public function turnOff()
    {
        $this->os->halt();
        $this->bios->powerDown();
    }
}