Implementing Decorator Pattern

Question

Context

I'm looking into design patterns. My first try is using the Decorator Pattern.

Question:

Is there another (maybe standard) approach to applying modifications in a decorator other than explicitly overwriting in the constructor? -

Car Interface

<?php

interface CarInterface 
{
    public function drive();
}

Care Base Class

<?php

class CarBaseClass implements CarInterface
{
    public $model = 'Base Model';
    public $top_speed = null;
    public $features = ['AC', 'Radio'];

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


    public function drive(): void
    {
        echo $this->model . " speed: " . $this->top_speed;
    }

}

Tesla

<?php

class Tesla extends CarBaseClass 
{
    public $model = 'Tesla';
}

Engine Feature Decorator

<?php

class V20Engine extends CarBaseClass
{
    public $SPEED_BOOST = 1.5;
    public $new_features = ['V20 Engine'];

    public function __construct(CarBaseClass $car) 
    {
        $this->model = 'V20 ' . $car->model;
        $this->top_speed = $car->top_speed * $this->SPEED_BOOST;;
        $this->features = array_merge($car->features, $this->new_features);
    }
}

Turbo Decorator

<?php

class TurboEnabled extends CarBaseClass 
{   
    public $TURBO_BOOST = 1.75;
    public $new_features = ['Turbo Enabled', 'Snoop Dog GPS'];

    public function __construct(CarBaseClass $car)
    {
        $this->model = 'Turbo Enabled ' . $car->model;
        $this->top_speed = $car->top_speed;
        $this->features = array_merge($car->features, $this->new_features);
    }

    public function activateTurbo() {
        $this->top_speed = $this->top_speed * $this->TURBO_BOOST;

        return $this;
    }
}

index.php

<?php 

require 'classes/Car/CarInterface.php';
require 'classes/Car/CarBaseClass.php';
require 'classes/Car/Tesla.php';
require 'classes/Car/Feature/TurboEnabled.php';
require 'classes/Car/Feature/V20Engine.php';

echo "<pre>";

$tesla = new Tesla(100);
$tesla->drive();

echo "<br>";

$turbo_tesla = new TurboEnabled($tesla);
$turbo_tesla->activateTurbo()->drive();

echo "<br>";

$v20_tesla = new V20Engine($tesla);
$v20_tesla->drive();

echo "<br>";

$v20_turbo_tesla = new V20Engine($turbo_tesla);
$v20_turbo_tesla->drive();

echo "<br>";

$car = new V20Engine( new TurboEnabled( new CarBaseClass(100) ) );
print_r( $car->features );

Answer 1

Decorators usually add more functional behaviors so if you had a method drive and TurboClass has a new functionality driveFast, you could probably call the Cars driveFast and then the some other special logic which turboClass has to do eg. checkTyres after driving fast. Here since you want the object construction to do it, this is the right way.

Answer 2

"overriding in the constructor" seems contrary to the decorator pattern See this description. Note "both the class of the object being modified and the class of the decorator share a base class" Perhaps a DecoratorBaseClass will solve the problem.