aidan Fri Oct 29 07:28:28 2004 EDT
Added files:
/phpdoc/en/language/oop5 patterns.xml
Log:
Added patterns section
http://cvs.php.net/co.php/phpdoc/en/language/oop5/patterns.xml?r=1.1&p=1
Index: phpdoc/en/language/oop5/patterns.xml
+++ phpdoc/en/language/oop5/patterns.xml
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.1 $ -->
<sect1 id="language.oop5.patterns">
<title>Patterns</title>
<para>
Patterns are ways to describe best practices and good designs.
They show a flexible solution to common programming problems.
</para>
<sect2>
<title>Factory</title>
<para>
The Factory pattern allows for the instantation of objects
at runtime. It is called a Factory Pattern since it is
responsible for "manufacturing" an object.
</para>
<example>
<title>Factory Method</title>
<programlisting role="php">
<![CDATA[
<?php
class DB {
// ... Other methods
// The Factory Method
function &factory($type)
{
if (include_once 'Drivers/' . $type . '.php') {
$classname = 'Driver_' . $type;
return new $classname;
} else {
throw new Exception ('Driver not found');
}
}
}
?>
]]>
</programlisting>
<para>
Defining this method in a class allows drivers to be loaded on the
fly. Loading a <literal>MySQL</literal> and a
<literal>SQLite</literal> driver could be done as follows:
</para>
<programlisting role="php">
<![CDATA[
<?php
// Load a MySQL Driver
$db_mysql = DB::factory('MySQL');
// Load a SQLite Driver
$db_sqlite = DB::factory('SQLite');
?>
]]>
</programlisting>
</example>
</sect2>
<sect2>
<title>Singleton</title>
<para>
The Singleton pattern applies to situations in which
there needs to be a single instance of a class.
The most common example of this is a database connection.
Implementing this pattern allows a programmer to make this
single instance easily accessible by many other objects.
</para>
<example>
<title>Singleton Function</title>
<programlisting role="php">
<![CDATA[
<?php
function &singleton($class)
{
// Declare a static variable to hold the object instance
static $instance;
// If the instance is not there create one
if (!isset($instance)) {
$instance = new $class;
}
return($instance);
}
?>
]]>
</programlisting>
<para>
This allows a single instance of any class to be retrieved.
Loading an example <literal>DB</literal> could be done like so:
</para>
<programlisting role="php">
<![CDATA[
<?php
$db = singleton('DB');
?>
]]>
</programlisting>
</example>
</sect2>
</sect1>
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