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<html><head><title>AutoLoader (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_04.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_06.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.5. AutoLoader</h2><p><a name="INDEX-1278" /><a name="INDEX-1279" /><a name="INDEX-1280" />Delays the loading of functions untilthey are used. Each function is placed in a file that has the samename as the function, with an<em class="emphasis">.al</em><a name="INDEX-1281" /> extension. Thefiles are stored in a subdirectory of the <em class="emphasis">auto/</em>directory that is named after the package. For example, the function<tt class="literal">GoodStuff::whatever</tt> is loaded from the file<em class="emphasis">auto/GoodStuff/whatever.al</em>. Should always be<tt class="literal">use</tt>d and not <tt class="literal">require</tt> d.</p><p>A module using the AutoLoader has the special marker, <tt class="literal">__END_ _</tt><a name="INDEX-1282" /> <a name="INDEX-1283" /> prior to thedeclarations for the subroutine to be autoloaded. Any code beforethis marker is loaded and compiled when the module is used, but atthe marker, Perl stops parsing the file.</p><p>Later, during execution, when a subroutine thatisn't yet in memory is called, the<tt class="literal">AUTOLOAD</tt> function attempts to find it in adirectory relative to the location of the module file. For example,if <em class="emphasis">POSIX.pm</em> is in the directory<em class="emphasis">/usr/local/lib/perl5</em>, then AutoLoader looks forPOSIX subroutines in<em class="emphasis">/usr/local/lib/perl5/auto/POSIX/*.al</em>.</p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_04.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_06.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.4. attrs</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.6. AutoSplit</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"><area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map></body></html>⌨️ 快捷键说明
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