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<html><head><title>Exporter (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_65.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_67.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.66. Exporter</h2><p><a name="INDEX-1398" />Implements adefault import method for other modules to inherit if theydon't want to define their own. If you are writing amodule, you can do the following:</p><blockquote><pre class="code">package <em class="replaceable"><tt>Module</tt></em>;use Exporter ( );@ISA = qw(Exporter);@EXPORT = qw(...); @EXPORT_OK = qw(...); %EXPORT_TAGS = (tag => [...]);</pre></blockquote><p>in which <tt class="literal">@EXPORT</tt> is a list of symbols to export bydefault, <tt class="literal">@EXPORT_OK</tt> is a list of symbols to exporton request, and <tt class="literal">%EXPORT_TAGS</tt> is a hash thatdefines names for sets of symbols. Names in<tt class="literal">%EXPORT_TAGS</tt> must also appear in<tt class="literal">@EXPORT</tt> or <tt class="literal">@EXPORT_OK</tt>.</p><p>Then Perl programs that want to use your module just say: </p><blockquote><pre class="code">use <em class="replaceable"><tt>Module</tt></em>; # Import default symbolsuse <em class="replaceable"><tt>Module</tt></em> qw(...); # Import listed symbolsuse <em class="replaceable"><tt>Module</tt></em> ( ); # Do not import any symbols</pre></blockquote><p>The Exporter can handle specialized import lists. An import list isthe list of arguments passed to the <tt class="literal">import</tt> method.If the first entry begins with <tt class="literal">!</tt>, :, or<tt class="literal">/</tt>, the list is treated as a series ofspecifications that add to or delete from the list. A leading<tt class="literal">!</tt> means delete, rather than add.</p><a name="ch08-110-fm2xml" /><table border="1" cellpadding="3"><tr><th><p>Symbol</p></th><th><p>Meaning</p></th></tr><tr><td><p><tt class="literal">[!]</tt><em class="replaceable"><tt>name</tt></em></p></td><td><p>This <em class="replaceable"><tt>name</tt></em> only</p></td></tr><tr><td><p><tt class="literal">[!]:DEFAULT</tt></p></td><td><p>All names in <tt class="literal">@EXPORT</tt></p></td></tr><tr><td><p><tt class="literal">[!]</tt>:<em class="replaceable"><tt>tag</tt></em></p></td><td><p>All names in<tt class="literal">$EXPORT_TAGS{</tt><em class="replaceable"><tt>tag</tt></em><tt class="literal">}</tt>anonymous list</p></td></tr><tr><td><p><tt class="literal">[!]/</tt><em class="replaceable"><tt>pattern</tt></em><tt class="literal">/</tt></p></td><td><p>All names in <tt class="literal">@EXPORT</tt> and<tt class="literal">@EXPORT_OK</tt> that match<em class="replaceable"><tt>pattern</tt></em></p></td></tr></table><p><p>Exporter's methods are the following.</p><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>export_fail</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre><em class="replaceable">module_name</em>->export_fail(<em class="replaceable">failed_symbols</em>)</pre><p>Returns a list of symbols that couldn't be imported.The default method provided by Exporter returns the list unchanged.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>export_ok_tags</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>export_ok_tags(<em class="replaceable">taglist</em>)</pre><p>Adds tagged sets of symbols to <tt class="literal">@EXPORT_OK</tt>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>export_tags</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>export_tags(<em class="replaceable">taglist</em>)</pre><p>Adds tagged sets of symbols to <tt class="literal">@EXPORT</tt>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>export_to_level</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre><em class="replaceable">package</em>->export_to_level(<em class="replaceable">n</em>, <em class="replaceable">what_to_export</em>)</pre><p>Used when you can't use Exporter'simport method directly. Takes the following arguments:</p><dl><dt><i><em class="replaceable"><tt>n</tt></em></i></dt><dd>An integer specifying how far up the calling stack to export yoursymbols</p></dd><dt><i><em class="replaceable"><tt>what_to_export</tt></em></i></dt><dd>Array of symbols to export, usually <tt class="literal">@_</tt></p></dd></dl></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>import</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>import</pre><p>The default import method.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>require_version</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre><em class="replaceable">module_name</em>->require_version(<em class="replaceable">value</em>)</pre><p>Validates the version of module<em class="replaceable"><tt>module_name</tt></em>, checking that it is at least<em class="replaceable"><tt>value</tt></em>.</p></div><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_65.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_67.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.65. Errno</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">8.67. ExtUtils::Command</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. 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