<?php

class Ratings implements IteratorAggregate {
  private $ratings;

  public function __construct(Rating ...$ratings) {
    $this->ratings = $ratings;
  }

  public function getAverage() : Rating {
    if (empty($this->ratings)) {
      return new Rating(0);
    }

    $total = 0;

    foreach ($this->ratings as $rating) {
      $total += $rating->getValue();
    }

    $average = $total / count($this->ratings);
    return new Rating($average);
  }

  public function getIterator() { /* ... */ }
}