PHP设计模式漫谈之迭代器模式(5)

注意，迭代器是比对象集更好的抽象，因为我们可以让InfiniteIterators，NoRewindIterators等，不用与普通数组阵列与一致，因此，Iterator缺少count()函数等功能。
在PHP官方手册中可以找到完整的SPL迭代器列表。得益于对PHP的强力支持，使用迭代器模式的大部分工作都包括在标准实现中，下面的代码示例就利用了标准Iterator和RecursiveIterators的功能。

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// lets play with RecursiveIterator implementations  $it = new RecursiveArrayIterator(array(      A,      B,      array(          C,          D      ),      array(          array(              E,              F          ),          array(              G,              H,              I          )      )  ));  // $it is a RecursiveIterator but also an Iterator,  // so it loops normally over the four elements  // of the array.  echo "Foreach over a RecursiveIterator: ";  foreach ($it as $value) {      echo $value;      // but RecursiveIterators specify additional      // methods to explore children nodes      $children = $it->hasChildren() ? {Yes} : {No};      echo $children, ;  }  echo " ";  // we can bridge it to a different contract via  // a RecursiveIteratorIterator, whose cryptic name  // should be read as an Iterator that spans over  // a RecursiveIterator.  echo "Foreach over a RecursiveIteratorIterator: ";  foreach (new RecursiveIteratorIterator($it) as $value) {      echo $value;  }  echo " "; 原文名：Practical Php Patterns: Iterator        作者：Giorgio

content; 
    private $_index = 0; 
 
    public function __construct(array $content) 
    { 
        $this->_content = $content; 
    } 
 
    public function rewind() 
    { 
        $this->_index = 0; 
    } 
 
    public function valid() 
    { 
        return isset($this->_content[$this->_index]); 
    } 
 
    public function current() 
    { 
        return $this->_content[$this->_index]; 
    } 
 
    public function key() 
    { 
        return $this->_index; 
    } 
 
    public function next() 
    { 
        $this->_index++; 
    } 
} 
 
$arrayarray = array(A, B, C, D); 
echo "Collection: "; 
foreach (new Collection($array) as $key => $value) { 
    echo "$key => $value. "; 
} 
echo " ";
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