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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_string.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_struct__tms.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 Struct</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><a href="#new">new</a> <a href="#new">new</a> <a href="#members">members</a> <a href="#_eq_eq"><i>==</i></a> <a href="#_ob_cb"><i>[ ]</i></a> <a href="#_ob_cb_eq"><i>[ ]=</i></a> <a href="#each"><i>each</i></a> <a href="#length"><i>length</i></a> <a href="#members"><i>members</i></a> <a href="#size"><i>size</i></a> <a href="#to_a"><i>to_a</i></a> <a href="#values"><i>values</i></a> <p></p><hr> <br><font size="-1">Subclasses: Struct::Tms</font><p></p>
<P></P>
A <code>Struct</code> is a convenient way to bundle a number of attributes
together, using accessor methods, without having to write an explicit
class.
<P></P>
The <code>Struct</code> class is a generator of specific classes, each one of
which is defined to hold a set of variables and their accessors. In
these examples, we'll call the generated class ``<i>Customer</i>Class,'' and
we'll show an example instance of that class as ``<i>Customer</i>Inst.''
<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>).<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">
mixins
</font></td></tr>
<tr><td>Enumerable:
</td><td>
collect, detect, each_with_index, entries, find, find_all, grep,
include?, map, max, member?, min, reject, select, sort, to_a</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="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
Struct.new( <i>[</i><i>aString</i><i>]</i> <i>[</i>, <i>aSym</i><i>]<sup>+</sup></i> )
-> <i>Customer</i>Class
</td></tr><td></td><td>
<P></P>
Creates a new class, named by <i>aString</i>, containing
accessor methods for the given symbols.
If the name <i>aString</i> is omitted, an anonymous structure
class will be created. Otherwise, the name of this struct will
appear as a constant in class <code>Struct</code>, so it must be unique
for all <code>Struct</code>s in the system and should start with a
capital letter.
<P></P>
<a href="ref_c_struct.html#new"><code>Struct::new</code></a> returns a new <code>Class</code> object, which can then be used
to create specific instances of the new structure.
The remaining methods listed below (class and instance) are
defined for this generated class. See the description that follows
for an example.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="new"><b>new</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Class.new( <i>[</i><i>anObject</i><i>]<sup>+</sup></i> )
-> <i>Customer</i>Inst
</td></tr><td></td><td>
<P></P>
Creates a new instance. The number of actual parameters must be
less than or equal to the number of attributes defined for this
class; unset parameters default to <code>nil</code>. Passing too many
parameters will raise an <code>ArgumentError</code>.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td valign="top"><code>joe.name</code></td>
<td valign="top"></td>
<td valign="top"><code>"Joe Smith"</code></td>
</tr>
<tr>
<td valign="top"><code>joe.zip</code></td>
<td valign="top"></td>
<td valign="top"><code>12345</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="members"><b>members</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Class.members
-> <i>anArray</i>
</td></tr><td></td><td>
<P></P>
Returns an array of strings representing the names of the
instance variables.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td valign="top"><code>Customer.members</code></td>
<td valign="top"></td>
<td valign="top"><code>["name", "address", "zip"]</code></td>
</tr>
</table>
<P></P>
<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="_eq_eq"><b>==</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst == <i>anOtherStruct</i>
-> <code>true</code> or <code>false</code>
</td></tr><td></td><td>
<P></P>
Equality---Returns <code>true</code> if <i>anOtherStruct</i> is equal to this
one: they must be of the same class as generated by
<a href="ref_c_struct.html#new"><code>Struct::new</code></a>, and the values of
all instance variables must be equal (according to
<a href="ref_c_object.html#_eq_eq"><code>Object#==</code></a>).
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joejr = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>jane = Customer.new( "Jane Doe", "456 Elm, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td valign="top"><code>joe == joejr</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>joe == jane</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="_ob_cb"><b>[ ]</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst[ <i>aSymbol</i> ] -> <i>anObject</i><br><i>Customer</i>Inst[ <i>anInteger</i> ] -> <i>anObject</i>
<P></P>
</td></tr><td></td><td>
<P></P>
Attribute Reference---Returns the value of the instance variable
named by <i>aSymbol</i>, or indexed (0..length-1) by
<i>anInteger</i>. Will raise <code>NameError</code> if the named
variable does not exist, or <code>IndexError</code> if the index is out of range.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td valign="top"><code>joe["name"]</code></td>
<td valign="top"></td>
<td valign="top"><code>"Joe Smith"</code></td>
</tr>
<tr>
<td valign="top"><code>joe[:name]</code></td>
<td valign="top"></td>
<td valign="top"><code>"Joe Smith"</code></td>
</tr>
<tr>
<td valign="top"><code>joe[0]</code></td>
<td valign="top"></td>
<td valign="top"><code>"Joe Smith"</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="_ob_cb_eq"><b>[ ]=</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst[ <i>aSymbol</i> ] = <i>anObject</i> -> <i>anObject</i><br><i>Customer</i>Inst[ <i>anInteger</i> ] = <i>anObject</i> -> <i>anObject</i>
<P></P>
</td></tr><td></td><td>
<P></P>
Attribute Assignment---Assigns to the instance variable named by
<i>aSymbol</i> or <i>anInteger</i>
the value <i>anObject</i> and returns it. Will raise
a <code>NameError</code> if the named variable does not exist, or an
<code>IndexError</code> if the index is out of range.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe["name"] = "Luke"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe[:zip] = "90210"</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td valign="top"><code>joe.name</code></td>
<td valign="top"></td>
<td valign="top"><code>"Luke"</code></td>
</tr>
<tr>
<td valign="top"><code>joe.zip</code></td>
<td valign="top"></td>
<td valign="top"><code>"90210"</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="each"><b>each</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst.each {| anObject | block }
<P></P>
-> <i>Customer</i>Inst
</td></tr><td></td><td>
<P></P>
Calls <i>block</i> once for each instance variable, passing the
value as a parameter.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Customer = Struct.new( "Customer", :name, :address, :zip )
joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )
joe.each {|x| puts(x) }
</pre></td></tr></table>
<em>produces:</em>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="400"><tr><td><pre>
Joe Smith
123 Maple, Anytown NC
12345
</pre></td></tr></table>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="length"><b>length</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst.length
-> <i>anInteger</i>
</td></tr><td></td><td>
<P></P>
Returns the number of instance variables.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td valign="top"><code>joe.length</code></td>
<td valign="top"></td>
<td valign="top"><code>3</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="members"><b>members</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst.members
-> <i>anArray</i>
</td></tr><td></td><td>
<P></P>
Returns an array of strings representing the names of the
instance variables.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td valign="top"><code>joe.members</code></td>
<td valign="top"></td>
<td valign="top"><code>["name", "address", "zip"]</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="size"><b>size</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst.size
-> <i>anInteger</i>
</td></tr><td></td><td>
<P></P>
Synonym for <a href="ref_c_struct.html#length"><code>Struct#length</code></a>.
<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>Customer</i>Inst.to_a
-> <i>anArray</i>
</td></tr><td></td><td>
<P></P>
Returns the values for this instance as an array.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>Customer = Struct.new( "Customer", :name, :address, :zip )</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )</code></td>
</tr>
<tr>
<td valign="top"><code>joe.to_a[1]</code></td>
<td valign="top"></td>
<td valign="top"><code>"123 Maple, Anytown NC"</code></td>
</tr>
</table>
<P></P>
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="values"><b>values</b></a></font></td><td bgcolor="#ffaaaa">
<i>Customer</i>Inst.values
-> <i>anArray</i>
</td></tr><td></td><td>
<P></P>
Synonym for <code>to_a</code>.
<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_string.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_struct__tms.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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