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
<?php
namespace 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
<?php
namespace 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
<?php
namespace Baobab;
/**
*修改图形颜色的装饰器
*/
class ColorDrawDecorator implements \Baobab\DrawDecorator{
protected $color;
function __construct($color = 'black'){
$this->color = $color;
} function beforeDraw(){
echo "<div style='color: {$this->color};'>";
}
function afterDraw(){
echo "</div>";
}
}
SizeDrawDecorator.php
<?php
namespace Baobab;
/**
*修改图形大小的装饰器
*/ class SizeDrawDecorator implements \Baobab\DrawDecorator{
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 Baobab\Canvas();
$canvas->init();
$canvas->rect(3, 6,4,12); $canvas->addDecorator(new \Baobab\ColorDrawDecorator('blue'));
$canvas->addDecorator(new \Baobab\SizeDrawDecorator('10px'));
......
//可添加其他更多装饰器
$canvas->draw();