Итератор (англ. Iterator) относится к классу шаблонов поведения. Используется в составных объектах. Предоставляет доступ к своим внутренним полям, не раскрывая их структуру.

Зачастую этот шаблон используется вместо массива объектов, чтобы не только предоставить доступ к элементам, но и наделить некоторой логикой. Это может быть ограничение доступа, сортировка или любая другая операция над множеством объектов.

Из коробки PHP, нам доступен интерфейс Iterator.

• Метод Iterator->current() возвращает текущий элемент
• Метод Iterator->next() перемещает указатель на следующий элемент
• Метод Iterator->key() возвращает индекс текущего элемента
• Метод Iterator->valid() проверяет, существует ли текущий элемент или нет
• Метод Iterator->rewind() переводит указатель текущего элемента на первый

• Worker.php

                
  <?php
  
  namespace DesignPatterns\Behavioral\Iterator;
  
  /**
   * Class Worker
   * @package DesignPatterns\Behavioral\Iterator
   */
  class Worker
  {
      /**
       * @var string
       */
      protected $name;
  
      /**
       * Worker constructor.
       *
       * @param string $name
       */
      public function __construct(string $name)
      {
          $this->name = $name;
      }
  
      /**
       * @return string
       */
      public function getName(): string
      {
          return $this->name;
      }
  }
  
                

• WorkersList.php

                
  <?php
  
  namespace DesignPatterns\Behavioral\Iterator;
  
  use Countable;
  use Iterator;
  
  /**
   * Class WorkersList
   * @package DesignPatterns\Behavioral\Iterator
   */
  class WorkersList implements Iterator, Countable
  {
  
      /**
       * @var Worker[]
       */
      protected $workers = [];
      /**
       * @var int
       */
      protected $currentIndex = 0;
  
      /**
       * @param Worker $worker
       */
      public function addWorker(Worker $worker)
      {
          $this->workers[] = $worker;
      }
  
      /**
       * @return Worker
       */
      public function current(): Worker
      {
          return $this->workers[$this->currentIndex];
      }
  
      /**
       * @return void
       */
      public function next()
      {
          $this->currentIndex++;
      }
  
      /**
       * @return int
       */
      public function key(): int
      {
          return $this->currentIndex;
      }
  
      /**
       * @return bool
       */
      public function valid(): bool
      {
          return isset($this->workers[$this->currentIndex]);
      }
  
      /**
       * @return void
       */
      public function rewind()
      {
          $this->currentIndex = 0;
      }
  
      /**
       * @return int
       */
      public function count(): int
      {
          return count($this->workers);
      }
  }
  
                

Test case:

IteratorTest.php

  
<?php

namespace DesignPatterns\Tests\Behavioral\Iterator;

use DesignPatterns\Behavioral\Iterator\Worker;
use DesignPatterns\Behavioral\Iterator\WorkersList;

class IteratorTest extends \PHPUnit_Framework_TestCase
{
    public function testWorkerGetName()
    {
        $name = 'TestName';

        $worker = new Worker($name);
        $this->assertEquals($name, $worker->getName());
    }

    public function testCountList()
    {
        $ivanWorker = new Worker('Ivan');
        $petrWorker = new Worker('Petr');
        $andreyWorker = new Worker('Andrey');

        $workersList = new WorkersList();

        $workersList->addWorker($ivanWorker);
        $workersList->addWorker($petrWorker);
        $workersList->addWorker($andreyWorker);
        $this->assertCount(3, $workersList);
    }

    public function testWorkersListKey()
    {
        $workersList = new WorkersList();

        $this->assertEquals(0, $workersList->key());

        $workersList->next();
        $this->assertEquals(1, $workersList->key());

        $workersList->next();
        $this->assertEquals(2, $workersList->key());
    }

    public function testWorkersListValid()
    {
        $ivanWorker = new Worker('Ivan');
        $petrWorker = new Worker('Petr');
        $andreyWorker = new Worker('Andrey');

        $workersList = new WorkersList();

        $workersList->addWorker($ivanWorker);
        $workersList->addWorker($petrWorker);
        $workersList->addWorker($andreyWorker);

        $this->assertEquals(true, $workersList->valid());

        $workersList->next();
        $this->assertEquals(true, $workersList->valid());

        $workersList->next();
        $this->assertEquals(true, $workersList->valid());

        $workersList->next();
        $this->assertEquals(false, $workersList->valid());
    }

    public function testWorkersListResetKey()
    {
        $workersList = new WorkersList();

        $this->assertEquals(0, $workersList->key());

        $workersList->next();
        $this->assertEquals(1, $workersList->key());

        $workersList->next();
        $this->assertEquals(2, $workersList->key());

        $workersList->rewind();
        $this->assertEquals(0, $workersList->key());
    }

    public function testWorkerListCurrentWorker()
    {
        $ivanWorker = new Worker('Ivan');
        $petrWorker = new Worker('Petr');
        $andreyWorker = new Worker('Andrey');

        $workersList = new WorkersList();

        $workersList->addWorker($ivanWorker);
        $workersList->addWorker($petrWorker);
        $workersList->addWorker($andreyWorker);

        $this->assertSame($ivanWorker, $workersList->current());
        $workersList->next();
        $this->assertSame($petrWorker, $workersList->current());
        $workersList->next();
        $this->assertSame($andreyWorker, $workersList->current());
        $workersList->rewind();
        $this->assertSame($ivanWorker, $workersList->current());
    }
}