使用Groovy的Adapter模式来处理遗留代码
如果使用Java语言，针对一个遗留的类Circle，需要建立一个接口，再建立新类和遗留类的适配器实现该接口，再建立一个控制器：
/**/
/*
?*?Adapter模式经常用来处理遗留代码
?*/
package
?com.XiongYi.designPatterns;
//遗留代码?Circle类?方法drawCircle()?这个类不便做更改
class?Circle...
{
????public?void?draw()...{
????????System.out.println("I'm?a?circle...");
????}
}
//
现要由于新的需要?要加入一些和Circle地位等价类，比如其中一个叫做Rect
//
并要让另一个扮演控制角色的Person类的方法draw()来统一操纵它们
//于是，创建接口Drawable，并让Circle的适配器和Rect的适配器代替他们各自工作
interface?Drawable...
{
????public?void?draw();
}
//再让原有Circle的适配器CircleAdapter实现Drawable
class?CircleAdapter?implements?Drawable...
{
????private?Circle?circle;
????public?CircleAdapter()...{
????????circle?=?new?Circle();
????}
????public?void?draw()?...{
????????circle.draw();
????}
}
//加入的Rect类
class?Rect...
{
????public?void?draw()...{
????????System.out.println("I'm?a?rect...");
????}
}
//同样也让Rect的适配器RectAdapter实现Drawable
class?RectAdapter?implements?Drawable...
{
????private?Rect?rect;
????public?RectAdapter()...{
????????rect?=?new?Rect();
????}
????public?void?draw()...{
????????rect.draw();
????}
}
//
最后扮演控制角色的Person类，
//它可以通过work方法根据传入的实现了Drawable接口的对象来统一控制它们工作了
class?Person...
{
????private?Drawable?drawable;
????public?Person(Drawable?drawable)...{
????????this.drawable?=?drawable;
????}
????public?void?work()...{
????????drawable.draw();
????}
}
public?class?Adapter?...
{
????public?static?void?main(String[]?args)...{
????????
????????new?Person(new?CircleAdapter()).work();
????????new?Person(new?RectAdapter()).work();
????????
????}
}
而使用Groovy的话，则变得超级简单：
package
?com.XiongYi.groovy.designPatters
//遗留代码?Circle类?方法drawCircle()?这个类不便做更改
class?Circle...
{
????def?draw()...{
????????println?"I'm?a?circle..."
????}
}
//现在加入Rect类
class?Rect...
{
????def?draw()...{
????????println?"I'm?a?rect..."
????}
}
//Person类扮演控制者的角色
class?Person...
{
????private?def?graphic
????Person(args)...{
????????graphic?=?args
????}
????def?draw()...{
????????try...{
????????????graphic.draw()
????????}catch(MissingMethodException?e)...{
????????????println?"U?can't?draw..."
????????}
????}
}
class?Adapter?...
{
????static?void?main(args)?...{
????????new?Person(new?Circle()).draw()
????????new?Person(new?Rect()).draw()
????}
}
可见，正是Groovy的动态语言特性，可以将类型判定一直延后到运行时进行，代码变得如此简单。
欢迎讨论。
