【设计模式】装饰器模式

使用场景： 当某一功能或方法draw，要满足不同的功能需求时，可以使用装饰器模式；实现方式：在方法的类中建addDecorator(添加装饰器),beforeDraw,afterDraw 3个新方法， 后2个分别放置在要修改的方法draw首尾.然后创建不同的装器类（其中要包含相同的,beforeDraw,afterDraw方法）能过addDecorator添加进去，然后在beforeDraw,afterDraw中循环处理，与观察者模式使用有点相似
1.装饰器模式（Decorator），可以动态地添加修改类的功能

2.一个类提供了一项功能，如果要在修改并添加额外的功能，传统的编程模式，需要写一个子类继承它，并重新实现类的方法

3.使用装饰器模式，仅需在运行时添加一个装饰器对象即可实现，可以实现最大的灵活性

DrawDecorator.php

 <?php  
namespace IMooc;  

interface DrawDecorator  
{  
    function beforeDraw();  
    function afterDraw();  
} 

Canvas.php

<?php  
namespace IMooc;  

class Canvas  
{  
    public $data;  
    protected $decorators = array();  

    //Decorator  
    function init($width = 20, $height = 10)  
    {  
        $data = array();  
        for($i = 0; $i < $height; $i++)  
        {  
            for($j = 0; $j < $width; $j++)  
            {  
                $data[$i][$j] = '*';  
            }  
        }  
        $this->data = $data;  
    }  

    function addDecorator(DrawDecorator $decorator)  
    {  
        $this->decorators[] = $decorator;  
    }  

    function beforeDraw()  
    {  
        foreach($this->decorators as $decorator)  
        {  
            $decorator->beforeDraw();  
        }  
    }  

    function afterDraw()  
    {  
        $decorators = array_reverse($this->decorators);  
        foreach($decorators as $decorator)  
        {  
            $decorator->afterDraw();  
        }  
    }  

    function draw()  
    {  
        $this->beforeDraw();  
        foreach($this->data as $line)  
        {  
            foreach($line as $char)  
            {  
                echo $char;  
            }  
            echo "<br />\n";  
        }  
        $this->afterDraw();  
    }  

    function rect($a1, $a2, $b1, $b2)  
    {  
        foreach($this->data as $k1 => $line)  
        {  
            if ($k1 < $a1 or $k1 > $a2) continue;  
            foreach($line as $k2 => $char)  
            {  
                if ($k2 < $b1 or $k2 > $b2) continue;  
                $this->data[$k1][$k2] = ' ';  
            }  
        }  
    }  
} 

ColorDrawDecorator.php

<?php  
namespace IMooc;  

class ColorDrawDecorator implements DrawDecorator  
{  
    protected $color;  
    function __construct($color = 'red')  
    {  
        $this->color = $color;  
    }  
    function beforeDraw()  
    {  
        echo "<div style='color: {$this->color};'>";  
    }  
    function afterDraw()  
    {  
        echo "</div>";  
    }  
} 

index.php

<?php  
define('BASEDIR', __DIR__);  
include BASEDIR.'/IMooc/Loader.php';  
spl_autoload_register('\\IMooc\\Loader::autoload');  

$canvas = new IMooc\Canvas();  
$canvas->init();  
$canvas->addDecorator(new \IMooc\ColorDrawDecorator('green'));  
$canvas->rect(3,6,4,12);  
$canvas->draw();