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预定义接口-迭代器Iterator

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发布: 2016-06-13 09:35:12
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<?<span>php

</span><span>/*</span><span>

可在内部迭代自己的外部迭代器或类的接口。

Iterator  extends Traversable  {

abstract public mixed current  ( void )

abstract public scalar key  ( void )

abstract public void next  ( void )

abstract public void rewind  ( void )

abstract public boolean valid  ( void )

}

</span><span>*/</span>

<span>class</span>  myIterator  <span>implements</span><span>  Iterator{

    </span><span>private</span>  <span>$position</span>  =  0<span> ;

    </span><span>private</span>  <span>$array</span>  = <span>array</span><span>(

         </span>"firstelement" ,

         "secondelement" ,

         "lastelement" ,<span>

    ); 

 

    </span><span>public</span> <span>function</span><span>  __construct () {

         </span><span>$this</span> -> position  =  0<span> ;

    }

 

    </span><span>function</span>  <span>rewind</span><span> () {

         </span><span>var_dump</span> ( <span>__METHOD__</span><span> );

         </span><span>$this</span> -> position  =  0<span> ;

    }

 

    </span><span>function</span>  <span>current</span><span> () {

         </span><span>var_dump</span> ( <span>__METHOD__</span><span> );

        </span><span>return</span>  <span>$this</span> -> <span>array</span> [ <span>$this</span> -><span> position ];

    }

 

    </span><span>function</span>  <span>key</span><span> () {

         </span><span>var_dump</span> ( <span>__METHOD__</span><span> );

         </span><span>return</span>  <span>$this</span> -><span> position ;

    }

 

    </span><span>function</span>  <span>next</span><span> () {

         </span><span>var_dump</span> ( <span>__METHOD__</span><span> );

        </span>++ <span>$this</span> -><span> position ;

         

    }

 

    </span><span>function</span><span>  valid () {

         </span><span>var_dump</span> ( <span>__METHOD__</span><span> );

        </span><span>return</span> <span>isset</span>( <span>$this</span> -> <span>array</span> [ <span>$this</span> -><span> position ]);

    }

}

 

 </span><span>$it</span>  = <span>new</span><span>  myIterator ;

 

</span><span>foreach</span>( <span>$it</span>  <span>as</span>  <span>$key</span>  =>  <span>$value</span><span> ) {

     </span><span>print_r</span>( <span>$key</span>.'/'.<span>$value</span><span> );

     </span><span>echo</span>  "<br />"<span> ;

}

 

</span><span>/*</span><span>

foreach循环第一次执行前,先调用rewind,返回到迭代器的第一个元素,开始位置也可控制

第二步执行valid检查当前位置是否有效,有效继续往下执行,无效则循环停止

第三步执行current返回当前元素的值

第四步执行key 返回当前元素的键

第五步:第一次循环结束后执行next向前移动到下一个元素开始下一轮的循环(紧接着跳过rewind,进行valid检测当前位置)

往下next,valid,current,key循环依次执行,直到valid到无效的位置

</span><span>*/</span>

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内容是自己总结的,有不对的地方,希望能指出!

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