PHP5对象迭代(Object Iteration)
PHP5提供一个为对象定义通过一连串的消息被重述的途径成为可能，例如使用一个foreach语句。默认地，所有可见的属性将用来迭代(反复)。
简单的对象迭代(Simple Object Iteration)
PHP代码如下:
<?php class MyClass { public $var1 = 'value 1'; public $var2 = 'value 2'; public $var3 = 'value 3'; protected $protected = 'protected var'; private $private = 'private var'; function iterateVisible() { echo "MyClass::iterateVisible:\n"; foreach($this as $key => $value){ print "$key => $value\n"; } } } $class = new MyClass(); foreach($class as $key => $value){ print "$key => $value\n"; } echo "\n"; $class->iterateVisible(); ?>
如输出显示，foreach重述能通过全部可见变量被访问。更进一步，你可以实现一个PHP5的指定的内在接口迭代器(Iterator)。允许对象描述什么是对象重述和对象如何被重述的。
迭代器实现对象迭代(Object Iteration implementing Iterator)
PHP代码如下:
<?php class MyIterator implements Iterator { private $var = array(); public function __construct($array) { if (is_array($array)){ $this->var = $array; } } public function rewind() { echo "rewinding\n"; reset($this->var); } public function current() { $var = current($this->var); echo "current: $var\n"; return $var; } public function key() { $var = key($this->var); echo "key: $var\n"; return $var; } public function next() { $var = next($this->var); echo "next: $var\n"; return $var; } public function valid() { $var = $this->current() !== false; echo "valid: {$var}\n"; return $var; } } $values = array(1,2,3); $it = new MyIterator($values); foreach ($it as $a => $b) { print "$a: $b\n"; } ?>
上例将输出：
rewinding current: 1 valid: 1 current: 1 key: 0 0: 1 next: 2 current: 2 valid: 1 current: 2 key: 1 1: 2 next: 3 current: 3 valid: 1 current: 3 key: 2 2: 3 next: current: valid:
在定义类时你也可以不必通过简单实现PHP5的IteratorAggregate接口定义所有的迭代器函数。
IteratorAggregate对象迭代实现
PHP代码如下:
<?php class MyCollection implements IteratorAggregate { private $items = array(); private $count = 0; // Required definition of interface IteratorAggregate public function getIterator() { return new MyIterator($this->items); } public function add($value) { $this->items[$this->count++] = $value; } } $coll = new MyCollection(); $coll->add('value 1'); $coll->add('value 2'); $coll->add('value 3'); foreach ($coll as $key => $val){ echo "key/value: [$key -> $val]\n\n"; } ?>
上例将输出：
rewinding current: value 1 valid: 1 current: value 1 key: 0 key/value: [0 -> value 1] next: value 2 current: value 2 valid: 1 current: value 2 key: 1 key/value: [1 -> value 2] next: value 3 current: value 3 valid: 1 current: value 3 key: 2 key/value: [2 -> value 3] next: current: valid:
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