对象迭代

对象迭代

Example #1 简单的对象迭代

<?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: ";
       foreach($this as $key => $value) {
           print "$key => $value ";
       }
    }
}

$class = new MyClass();

foreach($class as $key => $value) {
    print "$key => $value ";
}
echo " ";


$class->iterateVisible();

?>

以上例程会输出：

var1 => value 1
var2 => value 2
var3 => value 3

MyClass::iterateVisible:
var1 => value 1
var2 => value 2
var3 => value 3
protected => protected var
private => private var

如上所示,the foreach 遍历了所有 可见的 属性. 你也可以通过实现PHP 5自带的 Iterator接口来实现迭代. 使用Iterator接口可以让对象自行决定如何迭代自已。
 

Example #2 实现Iterator接口的迭代

<?php
class MyIterator implements Iterator
{
    private $var = array();

    public function __construct($array)
    {
        if (is_array($array)) {
            $this->var = $array;
        }
    }

    public function rewind() {
        echo "rewinding ";
        reset($this->var);
    }

    public function current() {
        $var = current($this->var);
        echo "current: $var ";
        return $var;
    }

    public function key() {
        $var = key($this->var);
        echo "key: $var ";
        return $var;
    }

    public function next() {
        $var = next($this->var);
        echo "next: $var ";
        return $var;
    }

    public function valid() {
        $var = $this->current() !== false;
        echo "valid: {$var} ";
        return $var;
    }
}

$values = array(1,2,3);
$it = new MyIterator($values);

foreach ($it as $a => $b) {
    print "$a: $b ";
}
?>

以上例程会输出：

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:

你也可以让类实现IteratorAggregate接口，这样你的类就不用强制性地实现 Iterator接口中的所有方法。

Example #3 通过IteratorAggregate来实现对象迭代

<?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] ";
}
?>

以上例程会输出：

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: