理解PHP的工厂模式Factory Pattern-php教程-PHP中文网

理解PHP的工厂模式Factory Pattern

高洛峰

发布： 2016-12-17 10:53:40

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1236人浏览过

工厂类就是一个专门用来创建其它对象的类，工厂类在多态性编程实践中是非常重要的。它允许动态替换类，修改配置，会使应用程序更加灵活。掌握工厂模式对web开发是必不可少的。

工厂模式通常用来返回类似接口的不同的类，工厂的一种常见用法就是创建多态的提供者。

通常工厂模式有一个关键的构造，即一般被命名为factory的静态方法。这个静态方法可以接受任意数量的参数，并且必须返回一个对象。

Program List：基本的工厂类

<?php
class Fruit {
// 对象从工厂类返回
}

Class FruitFactory {

public static function factory() {
// 返回对象的一个新实例
return new Fruit();
}
}

// 调用工厂
$instance = FruitFactory::factory();
?>

Program List：利用工厂类生产对象

立即学习“PHP免费学习笔记（深入）”；

<?php
class Example
{
// The parameterized factory method
public static function factory($type)
{
if (include_once 'Drivers/' . $type . '.php') {
$classname = 'Driver_' . $type;
return new $classname;
} else {
throw new Exception('Driver not found');
}
}
}
// Load a MySQL Driver
$mysql = Example::factory('MySQL');
// Load an SQLite Driver
$sqlite = Example::factory('SQLite');
?>

Program List：一个完整的工厂类

下面的程序定义了一个通用的工厂类，它生产能够保存你所有操作的空对象，你可以获得一个实例，这些操作都在那个实例中了。

<?php

/**
* Generic Factory class
*
* This Magic Factory will remember all operations you perform on it,
* and apply them to the object it instantiates.
*
*/
class FruitFactory {
private $history, $class, $constructor_args;

/**
* Create a factory of given class. Accepts extra arguments to be passed to
* class constructor.
*/
function __construct( $class ) {
$args = func_get_args();
$this->class = $class;
$this->constructor_args = array_slice( $args, 1 );
}

function __call( $method, $args ) {
$this->history[] = array(
'action' => 'call',
'method' => $method,
'args' => $args
);
}

function __set( $property, $value ) {
$this->history[] = array(
'action' => 'set',
'property' => $property,
'value' => $value
);
}

/**
* Creates an instance and performs all operations that were done on this MagicFactory
*/
function instance() {
# use Reflection to create a new instance, using the $args
$reflection_object = new ReflectionClass( $this->class );
$object = $reflection_object->newInstanceArgs( $this->constructor_args );

# Alternative method that doesn't use ReflectionClass, but doesn't support variable
# number of constructor parameters.
//$object = new $this->class();

# Repeat all remembered operations, apply to new object.
foreach( $this->history as $item ) {
if( $item['action'] == 'call' ) {
call_user_func_array( array( $object, $item['method'] ), $item['args'] );
}
if( $item['action'] == 'set' ) {
$object->{$item['property']} = $item['value'];
}
}

# Done
return $object;
}
}

class Fruit {
private $name, $color;
public $price;

function __construct( $name, $color ) {
$this->name = $name;
$this->color = $color;
}

function setName( $name ) {
$this->name = $name;
}

function introduce() {
print "Hello, this is an {$this->name} {$this->sirname}, its price is {$this->price} RMB.";
}
}

# Setup a factory
$fruit_factory = new FruitFactory('Fruit', 'Apple', 'Gonn');
$fruit_factory->setName('Apple');
$fruit_factory->price = 2;

# Get an instance
$apple = $fruit_factory->instance();
$apple->introduce();
?>