[php classes and objects] traversal

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Traversing objects

PHP 5 provides a way to define objects so that they can be traversed through a list of cells

By default, all visible properties will be used for traversal.

Example #1 简单的对象遍历（foreach 遍历所有其能够访问的可见属性。）<?phpclass MyClass{
    public $var1 = &#39;value 1&#39;;    public $var2 = &#39;value 2&#39;;    public $var3 = &#39;value 3&#39;;    
    protected $protected = &#39;protected var&#39;;    private   $private   = &#39;private var&#39;;    function iterateVisible() {
       echo "MyClass::iterateVisible:\n";       foreach($this as $key => $value) {           print "$key => $value\n";
       }
    }
}$class = new MyClass();foreach($class as $key => $value) {    print "$key => $value\n";
}echo "\n";$class->iterateVisible();?>

---

Implements the Iterator interface (predefined interface). You can let the object decide how to traverse and which values ​​are available each time it is traversed.

#接口摘要#Iterator extends Traversable {  

    abstract public mixed current ( void )  //返回当前索引游标指向的元素  

    abstract public scalar key ( void )   //返回当前索引游标指向的键  

    abstract public void next ( void )  //移动当前索引游标到下一元素 

    abstract public void rewind ( void )  //重置索引游标  

    abstract public boolean valid ( void )  //判断当前索引游标指向的元素是否有效  
}  

当一个实现了Iterator接口的对象，被foreach遍历时，会自动调用这些方法。

调用的循序是：rewind() -> valid() -> current() -> key() -> next()

Example #2 实现 Iterator 接口的对象遍历<?phpclass 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";
}?>

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