Hari 27: Immutability & Value Objects

Value Objects

readonly class Money {
    public function __construct(
        public readonly int    $amount,   // dalam sen
        public readonly string $currency,
    ) {}

    public function tambah(Money $other): self {
        if ($this->currency !== $other->currency) {
            throw new \InvalidArgumentException("Currency berbeda!");
        }
        return new self($this->amount + $other->amount, $this->currency);
    }

    public function kurang(Money $other): self {
        return new self($this->amount - $other->amount, $this->currency);
    }

    public function format(): string {
        return number_format($this->amount / 100, 2) . " " . $this->currency;
    }

    public function equals(Money $other): bool {
        return $this->amount === $other->amount && $this->currency === $other->currency;
    }
}

$harga    = new Money(50000, "IDR");
$diskon   = new Money(5000,  "IDR");
$final    = $harga->kurang($diskon);
echo $final->format() . "\n"; // 450.00 IDR