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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_bignum.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_class.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/).
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<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 Binding</font></td><td><table border="0"><tr><td><font color="white">
Parent:
</font></td><td><font color="white">Object</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><p></p><hr> Objects of class <code>Binding</code> encapsulate the execution context at some
particular place in the code and retain this context for future use.
The variables, methods, value of <code>self</code>, and possibly an iterator
block that can be accessed in this context are all retained.
Binding objects can be created using <a href="ref_m_kernel.html#binding"><code>Kernel#binding</code></a>, and are
made available to the callback of <a href="ref_m_kernel.html#set_trace_func"><code>Kernel#set_trace_func</code></a>.
<P></P>
These binding objects can be passed as the second argument of the
<a href="ref_m_kernel.html#eval"><code>Kernel#eval</code></a> method, establishing an environment for the
evaluation.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class Demo</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> def initialize(n)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> @secret = n</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> def getBinding</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> return binding()</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k1 = Demo.new(99)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b1 = k1.getBinding</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k2 = Demo.new(-3)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b2 = k2.getBinding</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td valign="top"><code>eval("@secret", b1)</code></td>
<td valign="top"></td>
<td valign="top"><code>99</code></td>
</tr>
<tr>
<td valign="top"><code>eval("@secret", b2)</code></td>
<td valign="top"></td>
<td valign="top"><code>-3</code></td>
</tr>
<tr>
<td valign="top"><code>eval("@secret")</code></td>
<td valign="top"></td>
<td valign="top"><code>nil</code></td>
</tr>
</table>
<P></P>
<P></P>
Binding objects have no class-specific methods.
<p></p><hr><table bgcolor="#a03030" cellpadding="10" border="0" cellspacing="0"><tr><td width="33%" align="left"><a class="subheader" href="ref_c_bignum.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_class.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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