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<html><title>Programming Ruby: The Pragmatic Programmer's Guide</title><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><STYLE TYPE="text/css"><!--
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</STYLE><table bgcolor="#a03030" cellpadding="3" border="0" cellspacing="0"><tr><td colspan="3"><table bgcolor="#902020" cellpadding="20"><tr><td><h1 class="header">Programming Ruby</h1><h3 class="subheader">The Pragmatic Programmer's Guide</h3></td></tr></table></td></tr><tr><td width="33%" align="left"><a class="subheader" href="ref_c_binding.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_continuation.html">Next ></a><br></td></tr></table></head><body bgcolor="white">
<!--
Copyright (c) 2001 by Addison Wesley Longman. This
material may be distributed only subject to the terms and
conditions set forth in the Open Publication License, v1.0 or
later (the latest version is presently available at
http://www.opencontent.org/openpub/).
-->
<table><tr><td height="20"><img src="dot.gif" width="1" height="20"></td></tr></table><table border="0" width="100%" bgcolor="660066" cellpadding="10"><tr><td valign="center"><font color="white" size="7">class Class</font></td><td><table border="0"><tr><td><font color="white">
Parent:
</font></td><td><font color="white">Module</font></td></tr><tr><td><font color="white">
Version:
</font></td><td><font color="white">
1.6
</font></td></tr></table></td></tr></table><p></p><H3>Index:</H3><a href="#inherited">inherited</a> <a href="#new">new</a> <a href="#new"><i>new</i></a> <a href="#superclass"><i>superclass</i></a> <p></p><hr>
<P></P>
Classes in Ruby are first-class objects---each is an instance of
class <code>Class</code>.
<P></P>
When a new class is created (typically using
<code>class Name ... end</code>), an object of type <code>Class</code> is created
and assigned to a global constant (<code>Name</code> in this case). When
<code>Name.new</code> is called to create a new object, the <code>new</code>
method in <code>Class</code> is run by default. This can be demonstrated by
overriding <code>new</code> in <code>Class</code>:
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
class Class
alias oldNew new
def new(*args)
print "Creating a new ", self.name, "\n"
oldNew(*args)
end
end
<P></P>
class Name
end
<P></P>
n = Name.new
</pre></td></tr></table>
<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Creating a new Name
</pre></td></tr></table>
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">class methods
</font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="inherited"><b>inherited</b></a></font></td><td bgcolor="#ffaaaa">
<i>aClass</i>.inherited( <i>aSubClass</i> )
</td></tr><td></td><td>
<P></P>
This is a singleton method (per class) invoked by Ruby when a subclass
of <i>aClass</i> is created. The new subclass is passed as a
parameter.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
class Top
def Top.inherited(sub)
print "New subclass: ", sub, "\n"
end
end
<P></P>
class Middle < Top
end
<P></P>
class Bottom < Middle
end
</pre></td></tr></table>
<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
New subclass: Middle
New subclass: Bottom
</pre></td></tr></table>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
Class.new( <i>aSuperClass</i>=<code>Object</code> )
-> <i>aClass</i>
</td></tr><td></td><td>
<P></P>
Creates a new anonymous (unnamed)
class with the given superclass (or
<code>Object</code> if no parameter is given).
<P></P>
</td></table>
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">instance methods
</font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
<i>aClass</i>.new( <i>[</i><i>args</i><i>]<sup>*</sup></i> )
-> <i>anObject</i>
</td></tr><td></td><td>
<P></P>
Creates a new object of <i>aClass</i>'s class, then invokes that object's
<code>initialize</code> method, passing it <i>args</i>.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="superclass"><b>superclass</b></a></font></td><td bgcolor="#ffaaaa">
<i>aClass</i>.superclass
-> <i>aSuperClass</i> or <code>nil</code>
</td></tr><td></td><td>
<P></P>
Returns the superclass of <i>aClass</i>, or <code>nil</code>.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>Class.superclass</code></td>
<td valign="top"></td>
<td valign="top"><code>Module</code></td>
</tr>
<tr>
<td valign="top"><code>Object.superclass</code></td>
<td valign="top"></td>
<td valign="top"><code>nil</code></td>
</tr>
</table>
<P></P>
<P></P>
</td></table>
<P></P>
<p></p><hr><table bgcolor="#a03030" cellpadding="10" border="0" cellspacing="0"><tr><td width="33%" align="left"><a class="subheader" href="ref_c_binding.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_c_continuation.html">Next ></a><br></td></tr></table><p></p><font size="-1">Extracted from the book "Programming Ruby -
The Pragmatic Programmer's Guide"</font><br><font size="-3">
Copyright
©
2000 Addison Wesley Longman, Inc. Released under the terms of the
<a href="http://www.opencontent.org/openpub/">Open Publication License</a> V1.0.
<br>
This reference is available for
<a href="http://www.pragmaticprogrammer.com/ruby/downloads/book.html">download</a>.
</font></body></html>
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