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。
<span>DrawDecorator</span>.php
<?<span>php namespace Baobab; </span><span>/*</span><span>* * 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 </span><span>*/</span> <span>interface</span><span> DrawDecorator{ </span><span>function</span><span> beforeDraw(); </span><span>function</span><span> afterDraw(); }</span>
<span>Canvas</span>.php
<?<span>php namespace Baobab; <br /><span>/**</span><br /><span>*Canvas类,绘制图形</span><br /><span>**/</span><br /> </span><span>class</span><span> Canvas { </span><span>public</span> <span>$data</span><span>; </span><strong><span>protected</span> <span>$decorators</span> = <span>array</span><span>(); </span></strong><span>//</span><span>Decorator</span> <span>function</span> init(<span>$width</span> = 20, <span>$height</span> = 10<span>) { </span><span>$data</span> = <span>array</span><span>(); </span><span>for</span>(<span>$i</span> = 0; <span>$i</span> < <span>$height</span>; <span>$i</span>++<span>) { </span><span>for</span>(<span>$j</span> = 0; <span>$j</span> < <span>$width</span>; <span>$j</span>++<span>) { </span><span>$data</span>[<span>$i</span>][<span>$j</span>] = '*'<span>; } } </span><span>$this</span>->data = <span>$data</span><span>; } </span><strong><span>function</span> addDecorator(DrawDecorator <span>$decorator</span><span>){ </span><span>$this</span>->decorators[] = <span>$decorator</span><span>; } </span><span>function</span><span> beforeDraw(){ </span><span>foreach</span>(<span>$this</span>->decorators <span>as</span> <span>$decorator</span><span>){ </span><span>$decorator</span>-><span>beforeDraw(); } } </span><span>function</span><span> afterDraw(){ </span><span>$decorators</span> = <span>array_reverse</span>(<span>$this</span>-><span>decorators); </span><span>foreach</span>(<span>$decorators</span> <span>as</span> <span>$decorator</span><span>){ </span><span>$decorator</span>-><span>afterDraw(); } } </span></strong><span>function</span><span> draw() { </span><strong><span>$this</span>-><span>beforeDraw(); </span></strong><span>foreach</span>(<span>$this</span>->data <span>as</span> <span>$line</span><span>) { </span><span>foreach</span>(<span>$line</span> <span>as</span> <span>$char</span><span>) { </span><span>echo</span> <span>$char</span><span>; } </span><span>echo</span> "<br />\n"<span>; } </span><strong><span>$this</span>-></strong><span><strong>afterDraw();</strong> } </span><span>function</span> rect(<span>$a1</span>, <span>$a2</span>, <span>$b1</span>, <span>$b2</span><span>) { </span><span>foreach</span>(<span>$this</span>->data <span>as</span> <span>$k1</span> => <span>$line</span><span>) { </span><span>if</span> (<span>$k1</span> < <span>$a1</span> or <span>$k1</span> > <span>$a2</span>) <span>continue</span><span>; </span><span>foreach</span>(<span>$line</span> <span>as</span> <span>$k2</span> => <span>$char</span><span>) { </span><span>if</span> (<span>$k2</span> < <span>$b1</span> or <span>$k2</span> > <span>$b2</span>) <span>continue</span><span>; </span><span>$this</span>->data[<span>$k1</span>][<span>$k2</span>] = ' '<span>; } } } }</span>
<span>ColorDrawDecorator</span>.php
<?<span>php namespace Baobab; <span>/**</span><br /><span>*修改图形颜色的装饰器</span><br /><span>*/ </span></span><span>class</span> ColorDrawDecorator <span>implements</span><span> \Baobab\DrawDecorator{ </span><span>protected</span> <span>$color</span><span>; </span><span>function</span> __construct(<span>$color</span> = 'black'<span>){ </span><span>$this</span>->color = <span>$color</span><span>; } </span><span>function</span><span> beforeDraw(){ </span><span>echo</span> "<div style='color: {<span>$this</span>->color};'>"<span>; }<br /> </span><span>function</span><span> afterDraw(){ </span><span>echo</span> "</div>"<span>; } }</span>
<span>SizeDrawDecorator</span>.php
<?<span>php namespace Baobab; <span><span>/**<br /><span>*修改图形大小的装饰器<br /><span>*/ </span></span></span></span> </span><span>class</span> SizeDrawDecorator <span>implements</span><span> \Baobab\DrawDecorator{ </span><span>protected</span> <span>$size</span><span>; </span><span>function</span> __construct(<span>$size</span> = '12px'<span>){ </span><span>$this</span>->size = <span>$size</span><span>; } </span><span>function</span><span> beforeDraw() { </span><span>echo</span> "<div style='font-size: {<span>$this</span>->size};'>"<span>; }<br /> </span><span>function</span><span> afterDraw() { </span><span>echo</span> "</div>"<span>; } }</span>
index.php
<span>$canvas</span> = <span>new</span><span> Baobab\Canvas(); </span><span>$canvas</span>-><span>init(); </span><span>$canvas</span>->rect(3, 6,4,12<span>); </span><span>$canvas</span>->addDecorator(<span>new</span> \Baobab\ColorDrawDecorator('blue'<span>)); </span><span>$canvas</span>->addDecorator(<span>new</span> \Baobab\SizeDrawDecorator('10px'<span>));<br />......<br />//可添加其他更多装饰器<br /> </span><span>$canvas</span>->draw();