<?php namespace Cron; use InvalidArgumentException; /** * CRON field factory implementing a flyweight factory * @link http://en.wikipedia.org/wiki/Cron */ class FieldFactory { /** * @var array Cache of instantiated fields */ private $fields = array(); /** * Get an instance of a field object for a cron expression position * * @param int $position CRON expression position value to retrieve * * @return FieldInterface * @throws InvalidArgumentException if a position is not valid */ public function getField($position) { if (!isset($this->fields[$position])) { switch ($position) { case 0: $this->fields[$position] = new MinutesField(); break; case 1: $this->fields[$position] = new HoursField(); break; case 2: $this->fields[$position] = new DayOfMonthField(); break; case 3: $this->fields[$position] = new MonthField(); break; case 4: $this->fields[$position] = new DayOfWeekField(); break; default: throw new InvalidArgumentException( $position . ' is not a valid position' ); } } return $this->fields[$position]; } }