装饰器模式，可以动态地添加修改类的功能。
一个类提供了一项功能，如果要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。使用装饰器模式，仅需要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<?phpnamespace Baobab;/** * Interface DrawDecorator * @package Baobab * 装饰器接口，定义两个方法,渲染画布之前和之后可添加额外的能力 */interface DrawDecorator{ function beforeDraw(); function afterDraw();}
Canvas.php<?phpnamespace Baobab;
/**
*Canvas类，绘制图形
**/
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<?phpnamespace Baobab;/**
*修改图形颜色的装饰器
*/class ColorDrawDecorator implements BaobabDrawDecorator{ protected $color; function __construct($color = 'black'){ $this->color = $color; } function beforeDraw(){ echo "<div style='color: {$this->color};'>"; }
function afterDraw(){ echo "</div>"; }}
SizeDrawDecorator.php<?phpnamespace Baobab;/**
*修改图形大小的装饰器
*/class SizeDrawDecorator implements BaobabDrawDecorator{ protected $size; function __construct($size = '12px'){ $this->size = $size; } function beforeDraw() { echo "<div style='font-size: {$this->size};'>"; }
function afterDraw() { echo "</div>"; }}
index.php
$canvas = new BaobabCanvas();$canvas->init();$canvas->rect(3, 6,4,12);$canvas->addDecorator(new BaobabColorDrawDecorator('blue'));$canvas->addDecorator(new BaobabSizeDrawDecorator('10px'));
......
//可添加其他更多装饰器
$canvas->draw();