mingw/html/lib/base.html

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   5 <title>base - Establish IS-A relationship with base classes at compile time</title>
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  13 <big><strong><span class="block">&nbsp;base - Establish IS-A relationship with base classes at compile time</span></strong></big>
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  17 <p><a name="__index__"></a></p>
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  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#diagnostics">DIAGNOSTICS</a></li>
  26         <li><a href="#history">HISTORY</a></li>
  27         <li><a href="#caveats">CAVEATS</a></li>
  28         <li><a href="#see_also">SEE ALSO</a></li>
  29 </ul>
  30 <!-- INDEX END -->
  31
  32 <hr />
  33 <p>
  34 </p>
  35 <h1><a name="name">NAME</a></h1>
  36 <p>base - Establish IS-A relationship with base classes at compile time</p>
  37 <p>
  38 </p>
  39 <hr />
  40 <h1><a name="synopsis">SYNOPSIS</a></h1>
  41 <pre>
  42     package Baz;
  43     use base qw(Foo Bar);</pre>
  44 <p>
  45 </p>
  46 <hr />
  47 <h1><a name="description">DESCRIPTION</a></h1>
  48 <p>Allows you to both load one or more modules, while setting up inheritance from
  49 those modules at the same time.  Roughly similar in effect to</p>
  50 <pre>
  51     package Baz;
  52     BEGIN {
  53         require Foo;
  54         require Bar;
  55         push @ISA, qw(Foo Bar);
  56     }</pre>
  57 <p>If any of the listed modules are not loaded yet, <em>base</em> silently attempts to
  58 <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_require"><code>require</code></a> them (and silently continues if the <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_require"><code>require</code></a> failed).  Whether to
  59 <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_require"><code>require</code></a> a base class module is determined by the absence of a global variable
  60 $VERSION in the base package.  If $VERSION is not detected even after loading
  61 it, &lt;base&gt; will define $VERSION in the base package, setting it to the string
  62 <code>-1, set by base.pm</code>.</p>
  63 <p>Will also initialize the fields if one of the base classes has it.
  64 Multiple inheritence of fields is <strong>NOT</strong> supported, if two or more
  65 base classes each have inheritable fields the 'base' pragma will
  66 croak.  See <a href="file://C|\msysgit\mingw\html/lib/fields.html">the fields manpage</a>, <em>public</em> and <em>protected</em> for a description of
  67 this feature.</p>
  68 <p>
  69 </p>
  70 <hr />
  71 <h1><a name="diagnostics">DIAGNOSTICS</a></h1>
  72 <dl>
  73 <dt><strong><a name="item_base_class_package__22_25s_22_is_empty_2e">Base class package ``%s'' is empty.</a></strong>
  74
  75 <dd>
  76 <p>base.pm was unable to require the base package, because it was not
  77 found in your path.</p>
  78 </dd>
  79 </li>
  80 </dl>
  81 <p>
  82 </p>
  83 <hr />
  84 <h1><a name="history">HISTORY</a></h1>
  85 <p>This module was introduced with Perl 5.004_04.</p>
  86 <p>
  87 </p>
  88 <hr />
  89 <h1><a name="caveats">CAVEATS</a></h1>
  90 <p>Due to the limitations of the implementation, you must use
  91 base <em>before</em> you declare any of your own fields.</p>
  92 <p>
  93 </p>
  94 <hr />
  95 <h1><a name="see_also">SEE ALSO</a></h1>
  96 <p><a href="file://C|\msysgit\mingw\html/lib/fields.html">the fields manpage</a></p>
  97 <table border="0" width="100%" cellspacing="0" cellpadding="3">
  98 <tr><td class="block" style="background-color: #cccccc" valign="middle">
  99 <big><strong><span class="block">&nbsp;base - Establish IS-A relationship with base classes at compile time</span></strong></big>
 100 </td></tr>
 101 </table>
 102
 103 </body>
 104
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