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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_numeric.html">Previous &lt;</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_proc.html">Next ></a><br></td></tr></table></head><body bgcolor="white">
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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 Object</font></td><td><table border="0"><tr><td><font color="white">
                Parent:
              </font></td><td><font color="white"></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="#_eq_eq"><i>==</i></a> <a href="#_eq_eq_eq"><i>===</i></a> <a href="#_eq_sd"><i>=~</i></a> <a href="#__id__"><i>__id__</i></a> <a href="#__send__"><i>__send__</i></a> <a href="#class"><i>class</i></a> <a href="#clone"><i>clone</i></a> <a href="#display"><i>display</i></a> <a href="#dup"><i>dup</i></a> <a href="#eql_qm"><i>eql?</i></a> <a href="#equal_qm"><i>equal?</i></a> <a href="#extend"><i>extend</i></a> <a href="#freeze"><i>freeze</i></a> <a href="#frozen_qm"><i>frozen?</i></a> <a href="#hash"><i>hash</i></a> <a href="#id"><i>id</i></a> <a href="#inspect"><i>inspect</i></a> <a href="#instance_eval"><i>instance_eval</i></a> <a href="#instance_of_qm"><i>instance_of?</i></a> <a href="#instance_variables"><i>instance_variables</i></a> <a href="#is_a_qm"><i>is_a?</i></a> <a href="#kind_of_qm"><i>kind_of?</i></a> <a href="#method"><i>method</i></a> <a href="#method_missing"><i>method_missing</i></a> <a href="#methods"><i>methods</i></a> <a href="#nil_qm"><i>nil?</i></a> <a href="#private_methods"><i>private_methods</i></a> <a href="#protected_methods"><i>protected_methods</i></a> <a href="#public_methods"><i>public_methods</i></a> <a href="#respond_to_qm"><i>respond_to?</i></a> <a href="#send"><i>send</i></a> <a href="#singleton_methods"><i>singleton_methods</i></a> <a href="#taint"><i>taint</i></a> <a href="#tainted_qm"><i>tainted?</i></a> <a href="#to_a"><i>to_a</i></a> <a href="#to_s"><i>to_s</i></a> <a href="#type"><i>type</i></a> <a href="#untaint"><i>untaint</i></a> <p></p><hr>
    <br><font size="-1">Subclasses: Array, Binding, Continuation,
    Data, Dir, Exception, FalseClass, File::Stat, Hash, IO,
    MatchingData, Method, Module, NilClass, Numeric, Proc, Range,
    Regexp, String, Struct, Symbol, Thread, Time, TrueClass</font><p></p>
<P></P>
  <code>Object</code> is the parent class of all classes in Ruby. Its methods
  are therefore available to all objects unless explicitly
  overridden.
<P></P>
  <code>Object</code> mixes in the <code>Kernel</code> module, making the built-in
  kernel functions globally accessible. Although the instance methods
  of <code>Object</code> are defined by the <code>Kernel</code> module, we have chosen
  to document them here for clarity.
<P></P>
  In the descriptions that follow, the
  parameter <i>aSymbol</i> refers to a symbol, which is either a
  quoted string or a <code>Symbol</code> (such as <code>:name</code>).
<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="_eq_eq"><b>==</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i> == <i>anObject</i>
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Equality---At the <code>Object</code> level, <code>==</code> returns <code>true</code> only if
      <i>obj</i> and <i>anObject</i> are the same object. Typically, this
      method is overridden in descendent classes to provide
      class-specific meaning.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_eq_eq_eq"><b>===</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i> === <i>anObject</i>
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Case Equality---A synonym for <a href="ref_c_object.html#_eq_eq"><code>Object#==</code></a>, but typically overridden by
      descendents to provide meaningful semantics in <code>case</code>
      statements.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_eq_sd"><b>=~</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i> =~ <i>anObject</i>
        -> <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Pattern Match---Overridden by descendents (notably <code>Regexp</code>
      and <code>String</code>) to provide meaningful
      pattern-match semantics.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="__id__"><b>__id__</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.__id__
        -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_object.html#id"><code>Object#id</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="__send__"><b>__send__</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.__send__(
        <i>aSymbol</i> <i>[</i>, <i>args</i><i>]<sup>+</sup></i> ) -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_object.html#send"><code>Object#send</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="class"><b>class</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.class -> <i>aClass</i>
      </td></tr><td></td><td>
<P></P>
      Returns the class of <i>obj</i> (synonym for <a href="ref_c_object.html#type"><code>Object#type</code></a>). 
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="clone"><b>clone</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.clone -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Produces a shallow copy of <i>obj</i>---the instance variables of <i>obj</i>
      are copied, but not the objects they reference. 
      Copies the frozen and tainted state of <i>obj</i>. See also the
      discussion under <a href="ref_c_object.html#dup"><code>Object#dup</code></a>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;attr_accessor&nbsp;:str</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
  <td valign="top"><code>s1&nbsp;=&nbsp;Klass.new</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Klass:0x4018d234></code></td>
</tr>
<tr>
  <td valign="top"><code>s1.str&nbsp;=&nbsp;"Hello"</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello"</code></td>
</tr>
<tr>
  <td valign="top"><code>s2&nbsp;=&nbsp;s1.clone</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Klass:0x4018d194&nbsp;&nbsp;@str="Hello"></code></td>
</tr>
<tr>
  <td valign="top"><code>s2.str[1,4]&nbsp;=&nbsp;"i"</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"i"</code></td>
</tr>
<tr>
  <td valign="top"><code>s1.inspect</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"#&lt;Klass:0x4018d234&nbsp;&nbsp;@str=\"Hi\">"</code></td>
</tr>
<tr>
  <td valign="top"><code>s2.inspect</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"#&lt;Klass:0x4018d194&nbsp;&nbsp;@str=\"Hi\">"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="display"><b>display</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.display( <i>port</i>=<code>$></code> )
        -> <code>nil</code>
      </td></tr><td></td><td>
<P></P>
      Prints <i>obj</i> on the given port (default <code>$></code>). Equivalent 
      to:
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
def&nbsp;display(port=$>)
&nbsp;&nbsp;port.write&nbsp;self
end
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="dup"><b>dup</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.dup -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Produces a shallow copy      
      of <i>obj</i>---the instance variables of <i>obj</i>
      are copied, but not the objects they reference. <code>dup</code>
      copies the tainted state of <i>obj</i>. See also the
      discussion under <a href="ref_c_object.html#clone"><code>Object#clone</code></a>.
      In general,
      <code>clone</code> and <code>dup</code> may have different semantics in
      descendent classes. While <code>clone</code> is used to duplicate an 
      object, including its internal state, <code>dup</code> typically
      uses the class of the descendent object to create the new instance.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="eql_qm"><b>eql?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.eql?( <i>anObject</i> )
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>obj</i> and <i>anObject</i> have the
      same value. Used by <code>Hash</code> to test
      members for equality. For objects of class <code>Object</code>,
      <code>eql?</code> is synonymous with <code>==</code>. Subclasses
      normally continue this tradition, but there are
      exceptions. <code>Numeric</code> types, for example, perform type
      conversion across <code>==</code>, but not across <code>eql?</code>, so:
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>1&nbsp;==&nbsp;1.0</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>1.eql?&nbsp;1.0</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="equal_qm"><b>equal?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.equal?( <i>anObject</i> )
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>obj</i> and <i>anObject</i> have the
      same object ID. This method should
      not be overridden by subclasses.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;[&nbsp;'cat',&nbsp;'dog'&nbsp;]</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>b&nbsp;=&nbsp;[&nbsp;'cat',&nbsp;'dog'&nbsp;]</code></td>
</tr>
<tr>
  <td valign="top"><code>a&nbsp;==&nbsp;b</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>a.id&nbsp;==&nbsp;b.id</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>a.eql?(b)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>a.equal?(b)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="extend"><b>extend</b></a></font></td><td bgcolor="#ffaaaa">
                <i>obj</i>.extend( <i>[</i><i>aModule</i><i>]<sup>+</sup></i> )
        -> <i>obj</i>
      </td></tr><td></td><td>
<P></P>
      Adds to <i>obj</i> the instance methods from each module given as a parameter.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>module&nbsp;Mod</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;hello</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;"Hello&nbsp;from&nbsp;Mod.\n"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;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>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;hello</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;"Hello&nbsp;from&nbsp;Klass.\n"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;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>k&nbsp;=&nbsp;Klass.new</code></td>
</tr>
<tr>
  <td valign="top"><code>k.hello</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello&nbsp;from&nbsp;Klass.\n"</code></td>
</tr>
<tr>
  <td valign="top"><code>k.extend(Mod)</code></td>
  <td valign="top"></td>
  <td valign="top"><code>#&lt;Klass:0x4018d414></code></td>
</tr>
<tr>
  <td valign="top"><code>k.hello</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello&nbsp;from&nbsp;Mod.\n"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="freeze"><b>freeze</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.freeze -> <i>obj</i>
      </td></tr><td></td><td>
<P></P>
      Prevents further modifications to <i>obj</i>. A <code>TypeError</code>
      will be raised if modification is attempted. There is no way to
      unfreeze a frozen object.
      See also <a href="ref_c_object.html#frozen_qm"><code>Object#frozen?</code></a>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
a&nbsp;=&nbsp;[&nbsp;"a",&nbsp;"b",&nbsp;"c"&nbsp;]
a.freeze
a&nbsp;&lt;&lt;&nbsp;"z"
</pre></td></tr></table>

<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
prog.rb:3:in&nbsp;`&lt;&lt;':&nbsp;can't&nbsp;modify&nbsp;frozen&nbsp;array&nbsp;(TypeError)
	from&nbsp;prog.rb:3
</pre></td></tr></table>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="frozen_qm"><b>frozen?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.frozen? 
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns the freeze status of <i>obj</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;[&nbsp;"a",&nbsp;"b",&nbsp;"c"&nbsp;]</code></td>
</tr>
<tr>
  <td valign="top"><code>a.freeze</code></td>
  <td valign="top"></td>
  <td valign="top"><code>["a",&nbsp;"b",&nbsp;"c"]</code></td>
</tr>
<tr>
  <td valign="top"><code>a.frozen?</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="hash"><b>hash</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.hash -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Generates a <code>Fixnum</code> hash value for this object. This function 
      must have the property that <code>a.eql?(b)</code> implies <code>a.hash == 
        b.hash</code>. The hash value is used by class <code>Hash</code>.
      Any hash value that exceeds the
      capacity of a <code>Fixnum</code> will be truncated before being used.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="id"><b>id</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.id -> <i>aFixnum</i>
      </td></tr><td></td><td>
<P></P>
      Returns an integer identifier for <i>obj</i>. The same number will be 
      returned on all calls to <code>id</code> for a given object, and no
      two active objects will share an id. <a href="ref_c_object.html#id"><code>Object#id</code></a> is a
      different concept from the <code>:name</code> notation, which returns the
      symbol id of <code>name</code>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="inspect"><b>inspect</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.inspect -> <i>aString</i>
      </td></tr><td></td><td>
<P></P>
      Returns a string containing a human-readable representation of
      <i>obj</i>. If not overridden, uses the <code>to_s</code> method to generate
      the string.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>[&nbsp;1,&nbsp;2,&nbsp;3..4,&nbsp;'five'&nbsp;].inspect</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"[1,&nbsp;2,&nbsp;3..4,&nbsp;\"five\"]"</code></td>
</tr>
<tr>
  <td valign="top"><code>Time.new.inspect</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Sun&nbsp;Mar&nbsp;04&nbsp;23:29:19&nbsp;CST&nbsp;2001"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="instance_eval"><b>instance_eval</b></a></font></td><td bgcolor="#ffaaaa">
                    <i>obj</i>.instance_eval(<i>aString</i>
                                 <i>[</i>, <i>file</i>
                                         <i>[</i><i>line</i><i>]</i><i>]</i> )
                                -> <i>anObject</i><br><i>obj</i>.instance_eval {|  | block }
 -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Evaluates a string containing Ruby source code, or the given
      block, within the
      context of the receiver (<i>obj</i>). In order to set the context, the 
      variable <code>self</code> is set to <i>obj</i> while the code is
      executing, giving the code access to <i>obj</i>'s instance variables.
      In the version of <code>instance_eval</code> that takes a
      <code>String</code>, the optional second and third parameters supply a
      filename and starting line number that are used when reporting
      compilation errors.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;initialize</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;@secret&nbsp;=&nbsp;99</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k&nbsp;=&nbsp;Klass.new</code></td>
</tr>
<tr>
  <td valign="top"><code>k.instance_eval&nbsp;{&nbsp;@secret&nbsp;}</code></td>
  <td valign="top"></td>
  <td valign="top"><code>99</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="instance_of_qm"><b>instance_of?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.instance_of?( <i>aClass</i> ) 
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>obj</i> is an instance of the 
      given class. See also <a href="ref_c_object.html#kind_of_qm"><code>Object#kind_of?</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="instance_variables"><b>instance_variables</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.instance_variables
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns an array of instance variable names for the
      receiver.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="is_a_qm"><b>is_a?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.is_a?( <i>aClass</i> ) 
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_object.html#kind_of_qm"><code>Object#kind_of?</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="kind_of_qm"><b>kind_of?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.kind_of?( <i>aClass</i> ) 
        -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
              Returns <code>true</code> if <i>aClass</i> is the class of <i>obj</i>, or 
      if <i>aClass</i> is one of the superclasses of <i>obj</i> or modules included
      in <i>obj</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>a&nbsp;=&nbsp;Integer.new</code></td>
</tr>
<tr>
  <td valign="top"><code>a.instance_of?&nbsp;Numeric</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>a.instance_of?&nbsp;Integer</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>a.instance_of?&nbsp;Fixnum</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>a.instance_of?&nbsp;Comparable</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>a.kind_of?&nbsp;Numeric</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>a.kind_of?&nbsp;Integer</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
<tr>
  <td valign="top"><code>a.kind_of?&nbsp;Fixnum</code></td>
  <td valign="top"></td>
  <td valign="top"><code>false</code></td>
</tr>
<tr>
  <td valign="top"><code>a.kind_of?&nbsp;Comparable</code></td>
  <td valign="top"></td>
  <td valign="top"><code>true</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="method"><b>method</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.method( <i>aSymbol</i> )
        -> <i>aMethod</i>
      </td></tr><td></td><td>
<P></P>
      Looks up the named method as a receiver in <i>obj</i>, returning a
      <code>Method</code> object (or raising <code>NameError</code>). The <code>Method</code> object acts
      as a closure in <i>obj</i>'s object instance, so instance variables
      and the value of <code>self</code> remain available.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Demo</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;initialize(n)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;@iv&nbsp;=&nbsp;n</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;hello()</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;"Hello,&nbsp;@iv&nbsp;=&nbsp;#{@iv}"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;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>k&nbsp;=&nbsp;Demo.new(99)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>m&nbsp;=&nbsp;k.method(:hello)</code></td>
</tr>
<tr>
  <td valign="top"><code>m.call</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello,&nbsp;@iv&nbsp;=&nbsp;99"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>l&nbsp;=&nbsp;Demo.new('Fred')</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>m&nbsp;=&nbsp;l.method("hello")</code></td>
</tr>
<tr>
  <td valign="top"><code>m.call</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello,&nbsp;@iv&nbsp;=&nbsp;Fred"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="method_missing"><b>method_missing</b></a></font></td><td bgcolor="#ffaaaa">
                <i>obj</i>.method_missing( <i>aSymbol</i> <i>[</i>, <i>*args</i><i>]</i> )
        -> <i>anObject</i>
      </td></tr><td></td><td>
              Invoked by Ruby when <i>obj</i> is sent a message it cannot
      handle. <i>aSymbol</i> is the symbol for the method called,
      and <i>args</i> are any arguments that were passed to it. The
      example below creates a class <code>Roman</code>, which responds to methods
      with names consisting of roman numerals, returning the corresponding
      integer values.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
class&nbsp;Roman
&nbsp;&nbsp;def&nbsp;romanToInt(str)
&nbsp;&nbsp;&nbsp;&nbsp;#&nbsp;...
&nbsp;&nbsp;end
&nbsp;&nbsp;def&nbsp;method_missing(methId)
&nbsp;&nbsp;&nbsp;&nbsp;str&nbsp;=&nbsp;methId.id2name
&nbsp;&nbsp;&nbsp;&nbsp;romanToInt(str)
&nbsp;&nbsp;end
end
</pre></td></tr></table>

<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>r&nbsp;=&nbsp;Roman.new</code></td>
</tr>
<tr>
  <td valign="top"><code>r.iv</code></td>
  <td valign="top"></td>
  <td valign="top"><code>4</code></td>
</tr>
<tr>
  <td valign="top"><code>r.xxiii</code></td>
  <td valign="top"></td>
  <td valign="top"><code>23</code></td>
</tr>
<tr>
  <td valign="top"><code>r.mm</code></td>
  <td valign="top"></td>
  <td valign="top"><code>2000</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="methods"><b>methods</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.methods -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns a list of the names of methods publicly accessible in
      <i>obj</i>. This will include all the methods accessible in <i>obj</i>'s
      ancestors. 
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;kMethod()</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k&nbsp;=&nbsp;Klass.new</code></td>
</tr>
<tr>
  <td valign="top"><code>k.methods[0..9]</code></td>
  <td valign="top"></td>
  <td valign="top"><code>["kMethod",&nbsp;"instance_of?",&nbsp;"protected_methods",&nbsp;"inspect",&nbsp;"freeze",&nbsp;"dup",&nbsp;"__id__",&nbsp;"equal?",&nbsp;"send",&nbsp;"=="]</code></td>
</tr>
<tr>
  <td valign="top"><code>k.methods.length</code></td>
  <td valign="top"></td>
  <td valign="top"><code>38</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="nil_qm"><b>nil?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.nil? -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      All objects except <code>nil</code> return <code>false</code>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="private_methods"><b>private_methods</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.private_methods
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns a list of private methods accessible within <i>obj</i>. This
      will include the private methods in <i>obj</i>'s ancestors, along
      with any mixed-in module functions.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="protected_methods"><b>protected_methods</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.protected_methods
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns the list of protected methods accessible to <i>obj</i>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="public_methods"><b>public_methods</b></a></font></td><td bgcolor="#ffaaaa">
                <i>obj</i>.public_methods -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Synonym for <a href="ref_c_object.html#methods"><code>Object#methods</code></a>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="respond_to_qm"><b>respond_to?</b></a></font></td><td bgcolor="#ffaaaa">
                <i>obj</i>.respond_to?( <i>aSymbol</i>,
                            <i>includePriv</i>=<code>false</code> )
            -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if <i>obj</i> responds to the given
      method. Private methods are included in the search only if the
      optional second parameter evaluates to <code>true</code>.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="send"><b>send</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.send( <i>aSymbol</i>
        <i>[</i>, <i>args</i><i>]<sup>*</sup></i> ) -> <i>anObject</i>
      </td></tr><td></td><td>
<P></P>
      Invokes the method identified by <i>aSymbol</i>, passing it any
      arguments specified. You can use <code>__send__</code> if the
      name <code>send</code> clashes with an existing method in <i>obj</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;hello(*args)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;&nbsp;&nbsp;"Hello&nbsp;"&nbsp;+&nbsp;args.join('&nbsp;')</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k&nbsp;=&nbsp;Klass.new</code></td>
</tr>
<tr>
  <td valign="top"><code>k.send&nbsp;:hello,&nbsp;"gentle",&nbsp;"readers"</code></td>
  <td valign="top"></td>
  <td valign="top"><code>"Hello&nbsp;gentle&nbsp;readers"</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="singleton_methods"><b>singleton_methods</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.singleton_methods
        -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns an array of the names of singleton methods for <i>obj</i>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class&nbsp;Klass</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;def&nbsp;Klass.classMethod</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>&nbsp;&nbsp;end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>k&nbsp;=&nbsp;Klass.new</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>def&nbsp;k.sm()</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
  <td valign="top"><code>Klass.singleton_methods</code></td>
  <td valign="top"></td>
  <td valign="top"><code>["classMethod"]</code></td>
</tr>
<tr>
  <td valign="top"><code>k.singleton_methods</code></td>
  <td valign="top"></td>
  <td valign="top"><code>["sm"]</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="taint"><b>taint</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.taint -> <i>obj</i>
      </td></tr><td></td><td>
<P></P>
      Marks <i>obj</i> as tainted      
      (see Chapter 20, which begins on page 257).
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="tainted_qm"><b>tainted?</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.tainted? -> <code>true</code> or <code>false</code>
      </td></tr><td></td><td>
<P></P>
      Returns <code>true</code> if the object is tainted.
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="to_a"><b>to_a</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.to_a -> <i>anArray</i>
      </td></tr><td></td><td>
<P></P>
      Returns an array representation of <i>obj</i>. For
      objects of class <code>Object</code> and others that don't explicitly
      override the method, the return value is an array containing <code>self</code>.
<P></P>

<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
  <td valign="top"><code>self.to_a</code></td>
  <td valign="top"></td>
  <td valign="top"><code>[main]</code></td>
</tr>
<tr>
  <td valign="top"><code>"hello".to_a</code></td>
  <td valign="top"></td>
  <td valign="top"><code>["hello"]</code></td>
</tr>
<tr>
  <td valign="top"><code>Time.new.to_a</code></td>
  <td valign="top"></td>
  <td valign="top"><code>[19,&nbsp;29,&nbsp;23,&nbsp;4,&nbsp;3,&nbsp;2001,&nbsp;0,&nbsp;63,&nbsp;false,&nbsp;"CST"]</code></td>
</tr>
</table>
<P></P>

<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="to_s"><b>to_s</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.to_s -> <i>aString</i>
      </td></tr><td></td><td>
<P></P>
      Returns a string representing <i>obj</i>. The default <code>to_s</code>
      prints the object's class and an encoding of the object id. As a
      special case, the top-level object that is the initial execution 
      context of Ruby programs returns ``main.''
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="type"><b>type</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.type -> <i>aClass</i>
      </td></tr><td></td><td>
<P></P>
      Returns the class of <i>obj</i>. 
<P></P>
      </td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="untaint"><b>untaint</b></a></font></td><td bgcolor="#ffaaaa">
        <i>obj</i>.untaint -> <i>obj</i>
      </td></tr><td></td><td>
<P></P>
      Removes the taint from <i>obj</i>.
<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_numeric.html">Previous &lt;</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_proc.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
      &#169;
      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>