php設計模式之迭代器模式

1.概念介紹

1.迭代器模式：在不需要了解內部實作的前提下，遍歷一個聚合物件的內部元素。
2.相較於傳統的程式模式，迭代器模式可以隱藏遍歷元素的所需的操作。
3.這裡介紹的迭代器需要實作（implements）PHP SPL 裡面的Iterator,需要實作5個方法（current， next，valid，rewid，key）

2.程式碼展示

<code><span>namespace</span><span>brave</span><span>class</span><span>AllUser</span><span>implements</span> \<span>Iterator</span>
{
    //所有<span>user</span>的<span>id</span><span>protected</span> $<span>ids</span>;
    <span>//保存数据库查询的对象,如果有就不需要在次查询了，可使用注册模式</span><span>protected</span><span>$data</span> = <span>array</span>(); 
    <span>//表示迭代器当前的位置</span><span>protected</span><span>$index</span>;

    <span><span>function</span><span>__construct</span><span>()</span>
    {</span><span>$db</span> = Factory::getDatabase();
        <span>$result</span> = <span>$db</span>->query(<span>"select id from user"</span>);
        <span>$this</span>->ids = <span>$result</span>->fetch_all(MYSQLI_ASSOC);
    }

    <span>//获取当前用户对象</span><span><span>function</span><span>current</span><span>()</span>
    {</span><span>$id</span> = <span>$this</span>->ids[<span>$this</span>->index][<span>'id'</span>];
        <span>return</span> Factory::getUser(<span>$id</span>);
    }

    <span>//进入下一个索引</span><span><span>function</span><span>next</span><span>()</span>
    {</span><span>$this</span>->index ++;
    }

    <span>//检查当前是否有数据</span><span><span>function</span><span>valid</span><span>()</span>
    {</span><span>return</span><span>$this</span>->index < count(<span>$this</span>->ids);
    }

    <span>//使当前的指针回到开始位置</span><span><span>function</span><span>rewind</span><span>()</span>
    {</span><span>$this</span>->index = <span>0</span>;
    }

    <span>//获取当前的索引值</span><span><span>function</span><span>key</span><span>()</span>
    {</span><span>return</span><span>$this</span>->index;
    }

}</code>

3.執行程式碼

<code><span>//迭代器模式实例</span><span>$users</span> = <span>new</span> AllUser();
<span>foreach</span> (<span>$users</span><span>as</span><span>$user</span>) {
    var_dump(<span>$user</span>);
    <span>echo</span><span>'<hr>'</span>;
}</code>

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以上就介紹了php設計模式迭代器模式，包含了面向的內容，希望對PHP教學有興趣的朋友有幫助。