Flyweight

Flyweight is a creational design pattern that lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects instead of keeping all of the data in each object.

---

we need to create ten thousand orders for a customer

The problem

If we do it this way, we are wasting a lot of memory, repeating data, which is always from the same client, which we don't need

<?php
class Budget 
{
    public float $value;
    public int $items;
}

<?php
class Order
{
    public string $clientName;
    public \DateTimeInterface $endDate;
    public Budget $budget;
}

<?php
$orders = [];

for ($i = 0; $i < 10000; $i++) {

    $order = new Order();
    $order->clientName = md5((string) rand(1 , 100000));
    $order->budget = new Budget();
    $order->endDate = new DateTimeImmutable();

    $orders[] = $order;

}

echo memory_get_peak_usage();

The solution

Now, using the Flyweight pattern, we get data that doesn't change, and we don't need to recreate it every time, thus making the whole abstraction much faster

<?php
class OrderFlyweight
{
    public string $clientName;
    public \DateTimeInterface $endDate;
}

<?php
class Order
{
    public OrderTemplate $orderTemplate;
    public Budget $budget;
}

<?php
class OrderCreator
{
    private array $templates = [];

    public function createOrder(string $clientName, \DateTimeInterface $endDate, Budget $budget) : Order
    {
        $orderTemplate = $this->generateOrderTemplate($clientName, $endDate);
        $order = new Order();
        $order->orderTemplate = $orderTemplate;
        $order->budget = $budget;

        return $order;
    }

    private function generateOrderTemplate(string $clientName, \DateTimeInterface $endDate) : OrderTemplate
    {
        $hash = md5($clientName . $endDate->getTimestamp());

        if (!array_key_exists($hash, $this->templates)) {
            $template = new OrderTemplate();
            $template->clientName = $clientName;
            $template->endDate = $endDate;

            $this->templates[$hash] = $template;
        }

        return $this->templates[$hash];
    }
}

<?php
$orders = [];

$orderCreator = new OrderCreator();
$clientName = md5((string) rand(1 , 100000));
$date = new DateTimeImmutable();

for ($i = 0; $i < 10000; $i++) {

    $budget = new Budget();
    $order = $orderCreator->createOrder($clientName, $date, $budget);
    $orders[] = $order;

}

echo memory_get_peak_usage();

---

Installation for test

composer install

php wrong/test.php
php right/test.php