一天一个设计模式（14）——迭代器模式

在面向对象程序设计中，迭代器模式是一种设计模式，其中迭代器用于遍历容器并访问容器的元素。迭代器模式将算法与容器解耦; 在某些情况下，算法是特定容器必需的，因此不能解耦。

<?php

class RadioStation
{
    private $_frequency;

    public function __construct(float $frequency)
    {
        $this->_frequency = $frequency;
    }

    public function getFrequency(): float
    {
        return $this->_frequency;
    }
}

class StationList implements Countable, Iterator
{

    private $_stations = [];
    private $_counter;

    public function addStation(RadioStation $station)
    {
        $this->_stations[] = $station;
    }

    public function removeStation(RadioStation $station)
    {
        $key=array_search($station,$this->_stations);
        array_splice($this->_stations,$key,1);
    }

    public function count(): int
    {
        return count($this->_stations);
    }

    public function current()
    {
        return $this->_stations[$this->_counter];
    }

    public function next()
    {
        $this->_counter++;
    }

    public function key()
    {
        return $this->_counter;
    }

    public function valid()
    {
        return isset($this->_stations[$this->_counter]);
    }

    public function rewind()
    {
        $this->_counter = 0;
    }

}

$stationList=new StationList();
$stationList->addStation(new RadioStation(88));
$stationList->addStation(new RadioStation(89));
$stationList->addStation(new RadioStation(90));
$stationList->addStation(new RadioStation(91));
$stationList->removeStation(new RadioStation(89));
foreach ($stationList as $station){
    echo $station->getFrequency().PHP_EOL;
}