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<html><head><title>Tie::Hash (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_217.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_219.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.218. Tie::Hash</h2><p><a name="INDEX-1587" />Provides skeletal methods forhash-tying classes. Tie::Hash provides a <tt class="literal">new</tt>method, as well as the methods <tt class="literal">TIEHASH</tt>,<tt class="literal">EXISTS</tt>, and <tt class="literal">CLEAR</tt>. The<tt class="literal">new</tt> method is provided as backup in case a classhas no <tt class="literal">TIEHASH</tt> method.</p><p>To write your own tied hashes, the methods listed here are required.See the <em class="emphasis">perltie</em> manpage for more detailedinformation and for examples.</p><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>TIEHASH</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>TIEHASH <em class="replaceable">ClassName</em>, <em class="replaceable">list</em></pre><p>Constructor. Associates a new hash instance with class<em class="replaceable"><tt>ClassName</em>. <em class="replaceable">list</tt></em>is a list of additional arguments needed to complete the association.</p><blockquote><pre class="code">tie %hash, <em class="replaceable"><tt>ClassName</em>, <em class="replaceable">list</tt></em></pre></blockquote></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>CLEAR</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>CLEAR <em class="replaceable">this</em></pre><p>Clears all values from tied hash <em class="replaceable">this</em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>DELETE</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>DELETE <em class="replaceable">this</em>, <em class="replaceable">key</em></pre><p>Deletes <em class="replaceable">key</em> from tied hash<em class="replaceable"><tt>this</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>EXISTS</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>EXISTS <em class="replaceable">this</em>, <em class="replaceable">key</em></pre><p>Verifies that <em class="replaceable">key</em> exists for tied hash<em class="replaceable"><tt>this</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>FETCH</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>FETCH <em class="replaceable">this</em>, <em class="replaceable">key</em></pre><p>Retrieves value associated with <em class="replaceable">key</em> fortied hash <em class="replaceable"><tt>this</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>FIRSTKEY</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>FIRSTKEY <em class="replaceable">this</em></pre><p>Returns key/value pair for the first key in tied hash<em class="replaceable"><tt>this</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>NEXTKEY</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>NEXTKEY <em class="replaceable">this</em>, <em class="replaceable">lastkey</em></pre><p>Returns next key/value pair after <em class="replaceable">lastkey</em>for tied hash <em class="replaceable">this</em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>STORE</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>STORE <em class="replaceable">this</em>, <em class="replaceable">key</em>, <em class="replaceable">value</em></pre><p>Stores <em class="replaceable">value</em> into tied hash<em class="replaceable"><tt>this</tt></em> with key<em class="replaceable"><tt>key</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_217.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_219.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.217. Tie::Handle</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">8.219. Tie::Memoize </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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