subject_36369.htm

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序号：36369 发表者：火骆驼 发表日期：2003-04-14 17:23:45
<br>主题：由谁能看懂这段代吗？
<br>内容：#define PCLASSINFO(cls, par) \<BR>&nbsp;&nbsp;public: \<BR>&nbsp;&nbsp;&nbsp;&nbsp;static const char * Class() \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ return #cls; } \<BR>&nbsp;&nbsp;&nbsp;&nbsp;virtual const char * GetClass(unsigned ancestor = 0) const \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ return ancestor &gt; 0 ? par::GetClass(ancestor-1) : cls::Class(); } \<BR>&nbsp;&nbsp;&nbsp;&nbsp;virtual BOOL IsClass(const char * clsName) const \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ return strcmp(clsName, cls::Class()) == 0; } \<BR>&nbsp;&nbsp;&nbsp;&nbsp;virtual BOOL IsDescendant(const char * clsName) const \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ return strcmp(clsName, cls::Class()) == 0 || \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; par::IsDescendant(clsName); } \<BR>&nbsp;&nbsp;&nbsp;&nbsp;virtual Comparison CompareObjectMemoryDirect(const PObject &amp; obj) const \<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ return (Comparison)memcmp(this, &amp;obj, sizeof(cls)); } \<BR>&nbsp;&nbsp;&nbsp;&nbsp;PNEW_AND_DELETE_FUNCTIONS<BR><BR>几个问题：<BR>1、return #cls当中的#表示什么意思？<BR>2、这个define的作用是什么，定义的是一个类？<BR>3、
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<font color=red>答案被接受</font><br>回复者：neilgan 回复日期：2003-04-14 22:24:55
<br>内容：1. '#' is a pre-processor operator, its function is to change a variable into a string. For example:<BR>PCLASSINFO(DerivedClass,ParentClass)<BR>then: #cls will be "DerivedClass"<BR><BR>2. This is a macro definition. When you add a line "PCLASSINFO(DeviredClass,ParentClass)" in your class definition,it defines several functions for the devired class.<BR><BR>
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回复者：salamander 回复日期：2003-04-15 19:36:04
<br>内容：你怎么知道 '#' is a pre-processor operator? 那么#include 中的#怎么解释?<BR>我没有见到别的地方再使用过#.如果你肯定,请把它的定义讲清楚.<BR><BR>btw:What does the word "devired" mean? I'm sure you can not find the word in any dictionary.Maybe There is a mistake.<BR><BR>waiting for your echo.....
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回复者：jinz_di 回复日期：2003-04-15 22:19:09
<br>内容："devired" 应为 "derived"之误.<BR>#见msdn
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回复者：lvbin 回复日期：2003-04-16 11:13:59
<br>内容：The number-sign or “stringizing” operator (#) converts macro parameters (after expansion) to string constants. It is used only with macros that take arguments.
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