SPL迭代器的工作和代理模式OuterIterator

1.迭代器通过foreach语言结构来实现迭代,没有实现迭代器接口(Iterator)的普通对象使用foreach结构会遍历公共属性.

2.OuterIterator用于做为实际迭代器的代理(即代理模式)

3.OuterIterator有RecursiveIteratorIterator(平面化多维结构,数组等),LimitIterator,等

4.由于OuterIterator概念的代理性质,实际上可以将它们叠加在一起使用

例:

<?php
$array = array(
  "Hello", // Level 1
  array(
    "World" // Level 2
  ),
  array(
    "How", // Level 2
    array(
      "are", // Level 3
      "you" // Level 3
    )
  ),
  "doing?" // Level 1
);

// Create our Recursive data structure
$recursiveIterator = new RecursiveArrayIterator($array);

// Create our recursive iterator
$recursiveIteratorIterator = new RecursiveIteratorIterator($recursiveIterator);

// Create a limit iterator
$limitIterator = new LimitIterator($recursiveIteratorIterator, 2, 5);

// Iterate
foreach ($limitIterator as $key => $value) {
  $innerIterator = $limitIterator->getInnerIterator();
  echo "Depth: " .$innerIterator->getDepth() . PHP_EOL;
  echo "Key: " .$key . PHP_EOL;
  echo "Value: " .$value . PHP_EOL;
}
?>