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delegation�Q�委托）

蘑菇 — Thu, 06 Apr 2006 08:25:00 GMT

Delegation 定义�Q?br /> Delegation is a way of making composition as powerful for reuse as inheritance [Lie86, JZ91]. In delegation, two objects are involved in handling a request: a receiving object delegates operations to its delegate. This is analogous to subclasses deferring requests to parent classes. But with inheritance, an inherited operation can always refer to the receiving object through the this member variable in C++ and self in Smalltalk. To achieve the same effect with delegation, the receiver passes itself to the delegate to let the delegated operation refer to the receiver

我的理解�Q?/font>
    A 把外界传来的讯息" 转�?/span>" �l?/span>B �H�由B 处理之﹐我们�U?/span>A 委托B 。当一些事物互相沟通分工合作时常用妥托观念�?br />
值得注意的是�Q?br />delegate -----> delegatee
^ |
| indirection |
--------------------
delegate��自己（对象�Q�传�l�delegatee�Q��delegatee可以通过该对象执行那些委托的操作�?br />
举个例子�Q?br />    在某个框架的�l�成部分中，对窗口设计，可以支持��L��形状的窗口�?br />    开始的时候考虑是不是��用子�c�L��实现�Q�乍一看似乎是比较好的�Q�但是考虑到对�H�口来说形状只能是它的一��属性：�H�口不是一“种”�Ş状——窗口“有”�Ş状�?font size="1">�Q�引自《The Pragmatic Programmer》）所以采用委托的方式�?br />    �q�时�Q�我们定义一个被委托�Q�delegatee�Q�类Shape和一个委托（delegate�Q�类window�?br />public abstract class Shape{
    //....
    public abstract boolean overlaps(Shape s);
    public abstract int getArea();
}

public class window{
    private Shape shape;
    public window(Shape shape){
        this.shape = shape;
        ...
    }
    public void setShape(Shape shape){
        this.shape = shape;
        ...
    }
    public boolean overlaps(window w){
        return shape.overlaps(w);
    }
    public int getArea(){
        return shape.getArea();
    }
}
class引自《The Pragmatic Programmer》）

蘑菇 2006-04-06 16:25 发表评论

蘑菇 — Wed, 07 Sep 2005 03:28:00 GMT

在windows�pȝ��下，回�R换行�W�号是“\r\n”，但是在Linux�{�系�l�下是没有“\r”符��L��。在解析文本或其他格式的文�g内容�Ӟ��常常要碰到判定回车换行的地方�Q�这个时候就要注意既要判定“\r\n”又要判定“\n”�?BR>虽然可以直接取得当前�pȝ��的回车换行符��h��使用�Q�但是文件�ƈ不一定是在当前系�l�下生成的，所以保证两�U�回车换行符��L��兼容判定是必需的�?/FONT>

蘑菇 2005-09-07 11:28 发表评论

蘑菇 — Wed, 10 Aug 2005 07:37:00 GMT

SD描述挺烦琐的�Q�怎么办？��d��呗。直接易懂，�q�不用担心会错意�?BR>各种囑ְ��d��啦。先是什么系�l�结构图�Q�再来点数据�l�构图，�c�d��Q�类关系图，�U�程囄��{�都��不了啦。不�q�我�q�次学到一�U�画法挺好的�?BR>详细情况参见下图�?IMG height=19 src="http://www.tkk7.com/Emoticons/teeth_smile.gif" width=19 border=0>

蘑菇 2005-08-10 15:37 发表评论

蘑菇 — Fri, 22 Jul 2005 09:55:00 GMT

假设有文件A�Q�模块功能将A的内�Ҏ��取一部分出来�Q�写入文件B�?BR>不加思烦我就把所有内容写��C��个类里面��M��。后来和同事讨论�Q�结论是功能耦合太紧�?IMG height=20 src="http://www.tkk7.com/Emoticons/QQ/21.gif" width=20 border=0>�Q�所以又拆分�?个类�Q�读�Q�解析，写）�Q�再加一个Control。但是我�q�是有些疑问�Q�这个功能太独立了，其他地方都不会��用到�Q�而且也挺��单，虽然分开之后更符合徏模模式，但是一定要分得�q�么�l�么�Q�当�Ӟ��如果其他地方要用刎ͼ�我肯定会把他们分开的啦�?BR>本来�q�费了点心思，写了个handler�Q�分开了之后完全都没有用了�Q�有点伤心呢�?IMG height=19 src="http://www.tkk7.com/Emoticons/QQ/22.gif" width=19 border=0>

蘑菇 2005-07-22 17:55 发表评论