php設計模式 裝飾器模式

裝飾器模式，可以動態地添加修改類的功能。

一個類提供了一項功能，如果要修改並添加額外的功能，傳統的編程模式需要寫一個子類繼承它，並重新實現類的方法。使用裝飾器模式，僅需要在運行時添加一個裝飾器對象即可實現，可以實現最大的靈活性。

DrawDecorator.php

<?php
namespace Baobab;
/**
 * Interface DrawDecorator
 * @package Baobab
 * 裝飾器介面，定義兩個方法,渲染畫布之前和之後可添加額外的能力
 */
interface DrawDecorator{
    function beforeDraw();
    function afterDraw();
}

Canvas.php

<?php
namespace Baobab;

/**
*Canvas類，繪製圖形
**/

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] = '&nbsp;';
            }
        }
    }
}

ColorDrawDecorator.php

<?php
namespace Baobab;
/**
*修改圖形顏色的裝飾器
*/
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;
/**
*修改圖形大小的裝飾器
*/

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'));
......
//可添加其他更多裝飾器

$canvas->draw();