装饰器模式

定义：可以动态地添加修改类的功能

解析：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。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。

$canvas1 = new IMoocCanvas();
$canvas1->init();
$canvas1->addDecorator(new IMoocColorDrawDecorator('green'));
$canvas1->addDecorator(new IMoocSizeDrawDecorator('16px'));
$canvas1->rect(3,6,4,12);
$canvas1->draw();

<?php
namespace IMooc;

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

    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 ($this->decorators as $decorator)
        {
            $decorator->afterDraw();
        }
    }

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

<?php
namespace IMooc;

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

<?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>";
    }
}

<?php
namespace IMooc;

class SizeDrawDecorator implements DrawDecorator
{
    protected $size;
    function __construct($size = '14px')
    {
        $this->size = $size;
    }

    function beforeDraw()
    {
        echo "<div style='font-size:{$this->size}'";
    }

    function afterDraw()
    {
        echo "</div>";
    }
}

来自为知笔记(Wiz)