php聚合式迭代器的基础知识点及实例代码

说明

1、实现其他迭代器功能的接口，相当于在其他迭代器上安装一个外壳，只有一种方法。

2、聚合迭代器可以与许多迭代器结合，实现更高效的迭代。

实例

class MainIterator implements Iterator
{
    private $var = array();
    public function __construct($array)    //构造函数, 初始化对象数组
    {
        if (is_array($array)) {
        $this->var = $array;
        }
    }
 
    public function rewind() {   
        echo "rewinding\n";
        reset($this->var);    //将数组的内部指针指向第一个单元
    }
 
    public function current() {
        $var = current($this->var);    // 返回数组中的当前值
        echo "current: $var\n";
        return $var;
    }
 
    public function key() {
        $var = key($this->var);       //返回数组中内部指针指向的当前单元的键名
        echo "key: $var\n";
        return $var;
    }
 
    public function next() {
        $var = next($this->var);     //返回数组内部指针指向的下一个单元的值
        echo "next: $var\n";
        return $var;
    }
 
    public function valid() {
    return !is_null(key($this->var); //判断当前单元的键是否为空
    }
}

内容扩展:

<?php
class myData implements IteratorAggregate {
    public $property1 = "Public property one";
    public $property2 = "Public property two";
    public $property3 = "Public property three";

    public function __construct() {
        $this->property4 = "last property";
    }

    public function getIterator() {
        return new ArrayIterator($this);
    }
}

$obj = new myData;

foreach($obj as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}
?>

以上例程的输出类似于：

string(9) “property1”
string(19) “Public property one”

string(9) “property2”
string(19) “Public property two”

string(9) “property3”
string(21) “Public property three”

string(9) “property4”
string(13) “last property”