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📁 by Randal L. Schwartz and Tom Phoenix ISBN 0-596-00132-0 Third Edition, published July 2001. (See
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<html><head><title>UNIVERSAL (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 &amp; 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_227.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_229.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.228. UNIVERSAL</h2><p><a name="INDEX-1599" />Base class;all blessed references inherit from it:</p><blockquote><pre class="code">$sub = $obj-&gt;can('print');$yes = UNIVERSAL::isa($ref, "HASH");</pre></blockquote><p>Provides the following methods.</p><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>can</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sub</em> = $<em class="replaceable">obj</em>-&gt;can(<em class="replaceable">method</em>)</pre><p>Checks if object <tt class="literal">$</tt><em class="replaceable">obj</em>has a method <em class="replaceable">method</em>. If so, returns areference to the subroutine; otherwise, returns<tt class="literal">undef</tt>. Can be called as a static or object methodcall, or as a subroutine:</p><blockquote><pre class="code">$ref = UNIVERSAL::can(<em class="replaceable"><tt>val</em>, <em class="replaceable">method</tt></em>)</pre></blockquote><p>Returns a reference to the subroutine if<em class="replaceable"><tt>val</tt></em> is a blessed reference with a method<em class="replaceable"><tt>method</tt></em>, and <tt class="literal">undef</tt> if<em class="replaceable"><tt>val</tt></em> is not blessed or does not have<em class="replaceable"><tt>method</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>isa</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">io</em> = $<em class="replaceable">fd</em>-&gt;isa(<em class="replaceable">type</em>)</pre><p>Returns true if the reference is blessed into package<em class="replaceable"><tt>type</tt></em> or inherits from that package. Can becalled as a static or object method call, or as a subroutine:</p><blockquote><pre class="code">UNIVERSAL::isa(<em class="replaceable"><tt>val</em>, <em class="replaceable">type</tt></em>)</pre></blockquote><p>Returns true if the first argument is a reference and either of thefollowing is true:</p><ul><li><p><em class="replaceable"><tt>val</tt></em> is a blessed reference and is blessedinto package <em class="replaceable"><tt>type</tt></em> or inherits from package<em class="replaceable"><tt>type</tt></em>.</p></li><li><p><em class="replaceable"><tt>val</tt></em> is a reference to a<em class="replaceable"><tt>type</tt></em> of Perl variable (e.g.,<tt class="literal">'HASH'</tt>).</p></li></ul></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>VERSION</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>VERSION([<em class="replaceable">require</em>])</pre><p>Returns the value of the variable <tt class="literal">$VERSION</tt> in thepackage the object is blessed into. With<em class="replaceable"><tt>require</tt></em> specified,<tt class="literal">VERSION</tt> dies if the version of the package is notequal to or greater than the version specified in<em class="replaceable"><tt>require</tt></em>. Can be called as either a staticor object method call.</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_227.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_229.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.227. Time::tm</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">8.229. User::grent</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 &copy; 2002</a> O'Reilly &amp; Associates. 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