part2-observer.pkg

来自「视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.」· PKG 代码 · 共 100 行

<refentry id="{@id}">

 <refnamediv>
  <refname>Observer pattern</refname>
  <refpurpose>implementation of the observer pattern</refpurpose>
 </refnamediv>

 {@toc}

 <refsect1 id="{@id intro}">
  <title>Introduction</title>
  <para>
   The <classname>HTML_Progress_Observer</classname> class provides an implementation 
   of the observer pattern. In the content of the HTML_Progress package, they provide a mechanism 
   which you can examine each important event as it is happened. 
   This allows the implementation of special behaviour based on the value of the progress element.
  </para>
 </refsect1>

 <refsect1 id="{@id useit}">
  <title>Basic concept</title>
  <para>
   Creating a progress observer involves implementing a subclass of the 
   <classname>HTML_Progress_Observer</classname> class. The subclass must override the base class 
   <emphasis>HTML_Progress_Observer::notify</emphasis> method. This method is passed a hash 
   containing event name and progress value.
  </para>
  <para>
   Now we will learn how to catch and manage specific events and respond to them
   in a specific way.
  </para>
 </refsect1>

 <refsect1 id="{@id useit}">
  <title>Using Progress Observers</title>
  <para>
   <refsect2 id="{@id observer-basic}">
    <title>Basic Observer</title>
    <para>
     If you creates an instance <classname>HTML_Progress_Observer</classname> class without 
     subclass, then default behaviour is to to write events (setminimum, setmaximum, setvalue) 
     into a file <filename>progress_observer.log</filename> in current directory.
     <simpara>
      This file contains for each event observed a PHP serialize ({@link http://www.php.net/manual/en/function.serialize.php})
      output result.
     </simpara>
    </para>
    <example><title>Basic Observer</title>
     {@example observer_basic.php}
    </example>
    <para>
     Example above produces such results:
     <screen>
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:10;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:20;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:30;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:40;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:50;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:60;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:70;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:80;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:90;} 
a:2:{s:3:"log";s:8:"incValue";s:5:"value";i:100;} 
     </screen>
    </para>
   </refsect2>
   <refsect2 id="{@id observer-complex}">
    <title>Complex Observer</title>
    <para>
     In this example, we will produces a dual progress meter which will simulate
     a software installation. One progress bar (left side) for each file copy, and one progress
     bar (right side) for global progress.
     On each left bar loop (100%), right bar will be increased by 25%.
     <simpara>
      Example below will display something like :
     </simpara>
     <figure>
      <graphic fileref="../media/screenshots/observer_complex.png"></graphic>      
     </figure>
     <example><title>Complex Observer </title>
     {@example observer_complex.php}
    </example>
     Lets considers the most important lines:
     <simpara>
      The do-while loop (<emphasis>lines 128 to 135</emphasis>) manage the reinitialization
      of left bar PB1 when this one reachs 100%.
     </simpara>
     <simpara>
      Changes on right bar PB2 are made by notify method of <classname>Bar1Observer</classname> 
      class when event catched is "setValue" and value is equal zero (<emphasis>lines 24 to 27</emphasis>), 
      raised by {@tutorial dm.setvalue.pkg} method on <emphasis>line 131</emphasis>.
     </simpara>
    </para>
   </refsect2>
  </para>
 </refsect1>

</refentry>